RENTAL PROPERTIES - Real Estate Detail (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Real estate and accumulated depreciation
Encumbrances (First Mortgages)	$ 411,439,541
Initial Cost to Partnerships
Land	85,836,705
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	54,927,136
Gross Amount at Which Carried at Close of Period
Land	85,993,233
Building Improvements	354,503,664
Totals	440,496,897	$ 400,703,910	$ 400,588,242	$ 398,629,793
Accumulated Depreciation	170,691,951	$ 159,627,479	$ 149,233,040	$ 134,019,906
Buildings and improvements
Initial Cost to Partnerships
Building Improvements	$ 299,576,528
Buildings and improvements | Minimum
Gross Amount at Which Carried at Close of Period
Estimated useful lives	10 years
Buildings and improvements | Maximum
Gross Amount at Which Carried at Close of Period
Estimated useful lives	40 years
Other Categories of Assets | Minimum
Gross Amount at Which Carried at Close of Period
Estimated useful lives	5 years
Other Categories of Assets | Maximum
Gross Amount at Which Carried at Close of Period
Estimated useful lives	15 years
Boylston Downtown L.P. Residential Apartments Boston, Massachusetts
Real estate and accumulated depreciation
Encumbrances (First Mortgages)	$ 34,092,579
Initial Cost to Partnerships
Land	2,112,000
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	10,184,183
Gross Amount at Which Carried at Close of Period
Land	2,268,528
Building Improvements	18,777,292
Totals	21,045,820
Accumulated Depreciation	15,996,297
Boylston Downtown L.P. Residential Apartments Boston, Massachusetts | Buildings and improvements
Initial Cost to Partnerships
Building Improvements	8,593,109
Brookside Associates LLC Residential Apartments Woburn, Massachusetts
Real estate and accumulated depreciation
Encumbrances (First Mortgages)	6,175,000
Initial Cost to Partnerships
Land	684,000
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	542,225
Gross Amount at Which Carried at Close of Period
Land	684,000
Building Improvements	3,658,225
Totals	4,342,225
Accumulated Depreciation	2,951,648
Brookside Associates LLC Residential Apartments Woburn, Massachusetts | Buildings and improvements
Initial Cost to Partnerships
Building Improvements	3,116,000
Clovelly Apartments L.P. Residential Apartments Nashua, New Hampshire
Real estate and accumulated depreciation
Encumbrances (First Mortgages)	11,214,000
Initial Cost to Partnerships
Land	177,610
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	1,641,894
Gross Amount at Which Carried at Close of Period
Land	177,610
Building Improvements	3,120,253
Totals	3,297,863
Accumulated Depreciation	2,490,061
Clovelly Apartments L.P. Residential Apartments Nashua, New Hampshire | Buildings and improvements
Initial Cost to Partnerships
Building Improvements	1,478,359
Commonwealth 1137 L.P. Residential Apartments Boston, Massachusetts
Real estate and accumulated depreciation
Encumbrances (First Mortgages)	5,440,000
Initial Cost to Partnerships
Land	342,000
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	1,051,069
Gross Amount at Which Carried at Close of Period
Land	342,000
Building Improvements	2,418,738
Totals	2,760,738
Accumulated Depreciation	2,104,872
Commonwealth 1137 L.P. Residential Apartments Boston, Massachusetts | Buildings and improvements
Initial Cost to Partnerships
Building Improvements	1,367,669
Commonwealth 1144 L.P. Residential Apartments Boston, Massachusetts
Real estate and accumulated depreciation
Encumbrances (First Mortgages)	32,325,000
Initial Cost to Partnerships
Land	1,410,000
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	6,629,860
Gross Amount at Which Carried at Close of Period
Land	1,410,000
Building Improvements	12,294,676
Totals	13,704,676
Accumulated Depreciation	8,163,969
Commonwealth 1144 L.P. Residential Apartments Boston, Massachusetts | Buildings and improvements
Initial Cost to Partnerships
Building Improvements	5,664,816
Executive Apartments L.P. Residential Apartments Framingham, Massachusetts
Real estate and accumulated depreciation
Encumbrances (First Mortgages)	8,190,000
Initial Cost to Partnerships
Land	91,400
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	1,578,382
Gross Amount at Which Carried at Close of Period
Land	91,400
Building Improvements	2,318,742
Totals	2,410,142
Accumulated Depreciation	1,650,112
Executive Apartments L.P. Residential Apartments Framingham, Massachusetts | Buildings and improvements
Initial Cost to Partnerships
Building Improvements	740,360
Hamilton Battle Green LLC Residential Apartments Lexington, Massachusetts
Real estate and accumulated depreciation
Encumbrances (First Mortgages)	3,766,660
Initial Cost to Partnerships
Land	1,341,737
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	144,819
Gross Amount at Which Carried at Close of Period
Land	1,341,737
Building Improvements	8,602,316
Totals	9,944,053
Accumulated Depreciation	4,361,558
Hamilton Battle Green LLC Residential Apartments Lexington, Massachusetts | Buildings and improvements
Initial Cost to Partnerships
Building Improvements	8,457,497
Hamilton Cypress LLC Commercial-1031Exchange Brookline, Massachusetts
Initial Cost to Partnerships
Land	2,362,596
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	38,233
Gross Amount at Which Carried at Close of Period
Land	2,362,596
Building Improvements	4,652,218
Totals	7,014,814
Accumulated Depreciation	1,990,947
Hamilton Cypress LLC Commercial-1031Exchange Brookline, Massachusetts | Buildings and improvements
Initial Cost to Partnerships
Building Improvements	4,613,985
Hamilton Green Apartments Residential Apartments Andover, Massachusetts
Real estate and accumulated depreciation
Encumbrances (First Mortgages)	32,190,519
Initial Cost to Partnerships
Land	16,054,336
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	(8,068,975)
Gross Amount at Which Carried at Close of Period
Land	16,054,336
Building Improvements	36,725,463
Totals	52,779,799
Accumulated Depreciation	16,828,423
Hamilton Green Apartments Residential Apartments Andover, Massachusetts | Buildings and improvements
Initial Cost to Partnerships
Building Improvements	44,794,438
Hamilton Highlands LLC Residential Needham Massachusetts [Member]
Real estate and accumulated depreciation
Encumbrances (First Mortgages)	19,437,587
Initial Cost to Partnerships
Land	6,815,522
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	(2,215,754)
Gross Amount at Which Carried at Close of Period
Land	6,815,522
Building Improvements	25,046,333
Totals	31,861,855
Accumulated Depreciation	6,292,999
Hamilton Highlands LLC Residential Needham Massachusetts [Member] | Buildings and improvements
Initial Cost to Partnerships
Building Improvements	27,262,087
Hamilton Linewt LLC Commercial-1031 Exchange Newton, Massachusetts
Initial Cost to Partnerships
Land	884,042
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	134,615
Gross Amount at Which Carried at Close of Period
Land	884,042
Building Improvements	2,786,742
Totals	3,670,784
Accumulated Depreciation	1,132,827
Hamilton Linewt LLC Commercial-1031 Exchange Newton, Massachusetts | Buildings and improvements
Initial Cost to Partnerships
Building Improvements	2,652,127
Hamilton Oaks Associates LLC Residential Apartments Brockton, Massachusetts
Real estate and accumulated depreciation
Encumbrances (First Mortgages)	26,666,000
Initial Cost to Partnerships
Land	2,175,000
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	6,595,768
Gross Amount at Which Carried at Close of Period
Land	2,175,000
Building Improvements	18,920,768
Totals	21,095,768
Accumulated Depreciation	13,931,561
Hamilton Oaks Associates LLC Residential Apartments Brockton, Massachusetts | Buildings and improvements
Initial Cost to Partnerships
Building Improvements	12,325,000
Highland Street Apartments, L.P. Residential Apartments Lowell, Massachusetts
Real estate and accumulated depreciation
Encumbrances (First Mortgages)	3,960,000
Initial Cost to Partnerships
Land	156,000
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	423,539
Gross Amount at Which Carried at Close of Period
Land	156,000
Building Improvements	1,057,624
Totals	1,213,624
Accumulated Depreciation	860,541
Highland Street Apartments, L.P. Residential Apartments Lowell, Massachusetts | Buildings and improvements
Initial Cost to Partnerships
Building Improvements	634,085
Linhart L.P. Residential/Commercial Newton, Massachusetts
Initial Cost to Partnerships
Land	385,000
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	2,057,202
Gross Amount at Which Carried at Close of Period
Land	385,000
Building Improvements	3,597,202
Totals	3,982,202
Accumulated Depreciation	2,897,449
Linhart L.P. Residential/Commercial Newton, Massachusetts | Buildings and improvements
Initial Cost to Partnerships
Building Improvements	1,540,000
Mill Street Gardens Residential Apartments Woburn Massachusetts
Real estate and accumulated depreciation
Encumbrances (First Mortgages)	31,000,000
Initial Cost to Partnerships
Land	9,798,478
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	2,981,885
Gross Amount at Which Carried at Close of Period
Land	9,798,478
Building Improvements	46,550,797
Totals	56,349,275
Accumulated Depreciation	11,673,659
Mill Street Gardens Residential Apartments Woburn Massachusetts | Buildings and improvements
Initial Cost to Partnerships
Building Improvements	43,568,912
Mill Street Development Woburn Massachusetts
Initial Cost to Partnerships
Land	1,375,000
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	(599,087)
Gross Amount at Which Carried at Close of Period
Land	1,375,000
Building Improvements	525,913
Totals	1,900,913
Mill Street Development Woburn Massachusetts | Buildings and improvements
Initial Cost to Partnerships
Building Improvements	1,125,000
NERA Dean St. Associates LLC Residential Apartments Norwood, Massachusetts
Real estate and accumulated depreciation
Encumbrances (First Mortgages)	10,322,000
Initial Cost to Partnerships
Land	1,512,000
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	1,595,198
Gross Amount at Which Carried at Close of Period
Land	1,512,000
Building Improvements	7,296,678
Totals	8,808,678
Accumulated Depreciation	5,390,982
NERA Dean St. Associates LLC Residential Apartments Norwood, Massachusetts | Buildings and improvements
Initial Cost to Partnerships
Building Improvements	5,701,480
North Beacon 140 L.P. Residential Units Boston, Massachusetts
Real estate and accumulated depreciation
Encumbrances (First Mortgages)	12,683,000
Initial Cost to Partnerships
Land	936,000
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	2,379,219
Gross Amount at Which Carried at Close of Period
Land	936,000
Building Improvements	6,141,232
Totals	7,077,232
Accumulated Depreciation	5,653,863
North Beacon 140 L.P. Residential Units Boston, Massachusetts | Buildings and improvements
Initial Cost to Partnerships
Building Improvements	3,762,013
Olde English Apartments L.P. Residential Apartments Lowell, Massachusetts
Real estate and accumulated depreciation
Encumbrances (First Mortgages)	9,608,000
Initial Cost to Partnerships
Land	46,181
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	1,289,156
Gross Amount at Which Carried at Close of Period
Land	46,181
Building Improvements	2,167,479
Totals	2,213,660
Accumulated Depreciation	1,548,529
Olde English Apartments L.P. Residential Apartments Lowell, Massachusetts | Buildings and improvements
Initial Cost to Partnerships
Building Improvements	878,323
Redwood Hills L.P. Residential Units Worcester, Massachusetts
Real estate and accumulated depreciation
Encumbrances (First Mortgages)	17,105,000
Initial Cost to Partnerships
Land	1,200,000
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	5,821,846
Gross Amount at Which Carried at Close of Period
Land	1,200,000
Building Improvements	10,632,450
Totals	11,832,450
Accumulated Depreciation	8,159,479
Redwood Hills L.P. Residential Units Worcester, Massachusetts | Buildings and improvements
Initial Cost to Partnerships
Building Improvements	4,810,604
Residences at CaptainParkers LLC Residential Apartments Lexington, Massachusetts
Real estate and accumulated depreciation
Encumbrances (First Mortgages)	20,750,000
Initial Cost to Partnerships
Land	6,247,153
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	(74,870)
Gross Amount at Which Carried at Close of Period
Land	6,247,153
Building Improvements	24,879,907
Totals	31,127,060
Accumulated Depreciation	8,148,830
Residences at CaptainParkers LLC Residential Apartments Lexington, Massachusetts | Buildings and improvements
Initial Cost to Partnerships
Building Improvements	24,954,777
River Drive L.P. Residential Apartments Danvers, Massachusetts
Real estate and accumulated depreciation
Encumbrances (First Mortgages)	9,543,000
Initial Cost to Partnerships
Land	72,525
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	1,693,812
Gross Amount at Which Carried at Close of Period
Land	72,525
Building Improvements	2,281,589
Totals	2,354,114
Accumulated Depreciation	1,195,277
River Drive L.P. Residential Apartments Danvers, Massachusetts | Buildings and improvements
Initial Cost to Partnerships
Building Improvements	587,777
Riverside Apartments Condominium Units Massachusetts
Initial Cost to Partnerships
Land	23,346
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	151,971
Gross Amount at Which Carried at Close of Period
Land	23,346
Building Improvements	342,778
Totals	366,124
Accumulated Depreciation	299,913
Riverside Apartments Condominium Units Massachusetts | Buildings and improvements
Initial Cost to Partnerships
Building Improvements	190,807
School St Assoc LLC Residential Apartments Framingham, Massachusetts
Real estate and accumulated depreciation
Encumbrances (First Mortgages)	26,993,000
Initial Cost to Partnerships
Land	4,686,728
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	457,122
Gross Amount at Which Carried at Close of Period
Land	4,686,728
Building Improvements	19,204,033
Totals	23,890,761
Accumulated Depreciation	13,393,356
School St Assoc LLC Residential Apartments Framingham, Massachusetts | Buildings and improvements
Initial Cost to Partnerships
Building Improvements	18,746,911
WRF Associates LLC Strip Mall Framingham, Massachusetts
Real estate and accumulated depreciation
Encumbrances (First Mortgages)	5,954,546
Initial Cost to Partnerships
Land	3,280,000
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	490,262
Gross Amount at Which Carried at Close of Period
Land	3,280,000
Building Improvements	5,410,262
Totals	8,690,262
Accumulated Depreciation	4,101,814
WRF Associates LLC Strip Mall Framingham, Massachusetts | Buildings and improvements
Initial Cost to Partnerships
Building Improvements	4,920,000
WCB Associates LLC Residential Apartments Brockton, Massachusetts
Real estate and accumulated depreciation
Encumbrances (First Mortgages)	19,266,000
Initial Cost to Partnerships
Land	1,335,000
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	3,250,982
Gross Amount at Which Carried at Close of Period
Land	1,335,000
Building Improvements	10,816,483
Totals	12,151,483
Accumulated Depreciation	8,461,934
WCB Associates LLC Residential Apartments Brockton, Massachusetts | Buildings and improvements
Initial Cost to Partnerships
Building Improvements	7,565,501
Westgate Apartments Residential Units Burlington Massachusetts Member
Real estate and accumulated depreciation
Encumbrances (First Mortgages)	4,494,000
Initial Cost to Partnerships
Land	44,965
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	322,345
Gross Amount at Which Carried at Close of Period
Land	44,965
Building Improvements	4,801,032
Totals	4,845,997
Accumulated Depreciation	3,402,530
Westgate Apartments Residential Units Burlington Massachusetts Member | Buildings and improvements
Initial Cost to Partnerships
Building Improvements	4,478,687
Westgate Apartments LLC Residential Apartments Woburn, Massachusetts
Real estate and accumulated depreciation
Encumbrances (First Mortgages)	38,475,000
Initial Cost to Partnerships
Land	461,300
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	6,702,223
Gross Amount at Which Carried at Close of Period
Land	461,300
Building Improvements	9,126,859
Totals	9,588,159
Accumulated Depreciation	6,280,115
Westgate Apartments LLC Residential Apartments Woburn, Massachusetts | Buildings and improvements
Initial Cost to Partnerships
Building Improvements	2,424,636
Woodland Park Apartments LLC Newton Massachusetts
Real estate and accumulated depreciation
Encumbrances (First Mortgages)	21,788,650
Initial Cost to Partnerships
Land	9,114,334
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	(1,161,715)
Gross Amount at Which Carried at Close of Period
Land	9,114,334
Building Improvements	34,713,279
Totals	43,827,613
Accumulated Depreciation	10,321,309
Woodland Park Apartments LLC Newton Massachusetts | Buildings and improvements
Initial Cost to Partnerships
Building Improvements	35,874,994
353 Worcester Rd
Initial Cost to Partnerships
Land	3,415,051
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	1,187,232
Gross Amount at Which Carried at Close of Period
Land	3,415,051
Building Improvements	5,684,081
Totals	9,099,132
Accumulated Depreciation	429,322
353 Worcester Rd | Buildings and improvements
Initial Cost to Partnerships
Building Improvements	4,496,849
Shawmut Place [Member]
Initial Cost to Partnerships
Land	7,297,401
Cost Capitalized Subsequent to Acquisition
Improvements, Net of retirements	7,702,495
Gross Amount at Which Carried at Close of Period
Land	7,297,401
Building Improvements	19,952,220
Totals	27,249,621
Accumulated Depreciation	577,775
Shawmut Place [Member] | Buildings and improvements
Initial Cost to Partnerships
Building Improvements	$ 12,249,725