RENTAL PROPERTIES (Details)			9 Months Ended
	Jul. 14, 2023 USD ($) ft² property	Jan. 18, 2023 USD ($) ft²	Sep. 30, 2023 property	Sep. 30, 2023 item	Sep. 30, 2023 ft²	Sep. 30, 2023	Sep. 30, 2023 USD ($)	Aug. 23, 2023	Dec. 31, 2022 USD ($)	Sep. 30, 2022 property
RENTAL PROPERTIES
Number of commercial shopping centers | item				2
Rental properties
Total fixed assets							$ 443,479,786		$ 400,703,910
Less: Accumulated depreciation							(171,180,209)		(159,627,479)
Total fixed assets, net							272,299,577		241,076,431
Land, improvements and parking lots
Rental properties
Total fixed assets							98,563,951		87,405,897
Land, improvements and parking lots | Minimum
Rental properties
Useful Life			15 years
Land, improvements and parking lots | Maximum
Rental properties
Useful Life			40 years
Buildings and improvements
Rental properties
Total fixed assets							278,781,377		256,035,191
Buildings and improvements | Minimum
Rental properties
Useful Life			15 years
Buildings and improvements | Maximum
Rental properties
Useful Life			40 years
Kitchen cabinets
Rental properties
Total fixed assets							16,894,050		14,347,212
Kitchen cabinets | Minimum
Rental properties
Useful Life			5 years
Kitchen cabinets | Maximum
Rental properties
Useful Life			10 years
Carpets
Rental properties
Total fixed assets							13,984,498		12,047,573
Carpets | Minimum
Rental properties
Useful Life			5 years
Carpets | Maximum
Rental properties
Useful Life			10 years
Air conditioning
Rental properties
Total fixed assets							501,697		501,697
Air conditioning | Minimum
Rental properties
Useful Life			5 years
Air conditioning | Maximum
Rental properties
Useful Life			10 years
Laundry equipment
Rental properties
Total fixed assets							563,160		553,140
Laundry equipment | Minimum
Rental properties
Useful Life			5 years
Laundry equipment | Maximum
Rental properties
Useful Life			7 years
Elevators
Rental properties
Total fixed assets							1,885,265		1,885,265
Elevators | Minimum
Rental properties
Useful Life			20 years
Elevators | Maximum
Rental properties
Useful Life			40 years
Swimming pools
Rental properties
Total fixed assets							1,090,604		1,090,604
Swimming pools | Minimum
Rental properties
Useful Life			10 years
Swimming pools | Maximum
Rental properties
Useful Life			30 years
Equipment
Rental properties
Total fixed assets							20,951,525		18,716,758
Equipment | Minimum
Rental properties
Useful Life			5 years
Equipment | Maximum
Rental properties
Useful Life			30 years
Motor vehicles
Rental properties
Total fixed assets							232,954		171,519
Motor vehicles | Maximum
Rental properties
Useful Life			5 years
Fences
Rental properties
Total fixed assets							77,620		46,872
Fences | Minimum
Rental properties
Useful Life			5 years
Fences | Maximum
Rental properties
Useful Life			15 years
Furniture and fixtures
Rental properties
Total fixed assets							$ 9,953,085		$ 7,902,182
Furniture and fixtures | Minimum
Rental properties
Useful Life			5 years
Furniture and fixtures | Maximum
Rental properties
Useful Life			7 years
Wholly owned properties
RENTAL PROPERTIES
Number of properties | property			31
Investment Properties
RENTAL PROPERTIES
Number of units | property			865							865
NERA 40%
RENTAL PROPERTIES
Ownership interest (as a percent)						40.00%				40.00%
NERA 50%
RENTAL PROPERTIES
Ownership interest (as a percent)						50.00%		50.00%		50.00%
Residential and mixed-use properties
RENTAL PROPERTIES
Number of properties | property	3
Residential and mixed-use properties | Wholly owned properties
RENTAL PROPERTIES
Number of units | item				2,944
Number of properties | property			27
Residential and mixed-use properties | Wholly owned properties | Purchase and sale agreement | South End neighborhood of Boston, MA
RENTAL PROPERTIES
Number of units | property	52
Residential and mixed-use properties | Partially owned properties
RENTAL PROPERTIES
Number of units			688	688
Rental properties
Area of property (in square feet) | ft²					12,500
Residential and mixed-use properties | Investment Properties | Partially owned properties
RENTAL PROPERTIES
Number of properties | item				7
Residential and mixed-use properties | Limited Partnerships | Partially owned properties
RENTAL PROPERTIES
Number of properties | item				7
Residential and mixed-use properties | NERA 40% | Partially owned properties | Minimum
RENTAL PROPERTIES
Ownership interest (as a percent)						40.00%
Residential and mixed-use properties | NERA 50% | Partially owned properties | Maximum
RENTAL PROPERTIES
Ownership interest (as a percent)						50.00%
Condominium | Wholly owned properties
RENTAL PROPERTIES
Number of units | item				19
Number of properties | property			1
Commercial
Rental properties
Area of property (in square feet) | ft²	3,400
Purchase price	$ 27,500,000
Closing costs	$ 81,000
Commercial | Property located at 659 Worcester Road, Framingham, MA.
Rental properties
Purchase price		$ 10,151,000
Closing costs		$ 59,000
Commercial | Purchase and sale agreement | Property located at 659 Worcester Road, Framingham, MA.
Rental properties
Area of property (in square feet) | ft²		20,700
Commercial | Wholly owned properties
RENTAL PROPERTIES
Number of properties | property			4
Rental properties
Area of property (in square feet) | ft²					137,153
Commercial | Investment Properties
RENTAL PROPERTIES
Number of units | property			3							3