MORTGAGE NOTES PAYABLE (Line of Credit) (Details)					1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
	Jun. 04, 2018 USD ($)	Mar. 29, 2018 USD ($)	Sep. 30, 2015	Jul. 31, 2014 USD ($) item	Jul. 31, 2018 USD ($)	Aug. 31, 2014	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2005	Oct. 31, 2018 USD ($)	Sep. 29, 2017 USD ($)	Jul. 06, 2017 USD ($)	Mar. 07, 2005 item
Line of Credit
Interest expense							$ 3,090,471	$ 3,046,818	$ 9,331,023	$ 8,113,197
Payment on line of credit									12,000,000	$ 16,000,000
Credit line balance							5,000,000		5,000,000		$ 17,000,000
Line Of Credit Facility Unused Capacity Commitment Fee									15,000
Woodland Park Apartments LLC Newton Massachusetts
Line of Credit
Loan amount														$ 22,250,000	$ 16,000,000
Credit line balance											17,000,000				$ 25,000,000
Webster Green Apartments
Line of Credit
Loan amount		$ 21,500,000
Credit line balance		8,000,000
Hamilton Essex 81
Line of Credit
Number of properties in which borrowing amount collateralized | item																1
Minimum
Line of Credit
Tangible net worth							150,000,000		$ 150,000,000
Ratio of net operating income to total indebtedness									9.50%
Debt service coverage ratio									1.6
Maximum
Line of Credit
Leverage ratio									65.00%
Aggregate increase in indebtedness									$ 15,000,000
Mortgages payable | Hamilton Essex 81
Line of Credit
Term of debt			10 years
Mortgages payable | Hamilton on Main Apartments, LLC
Line of Credit
Term of debt						10 years						10 years
Mortgages payable | LIBOR | Hamilton Essex 81
Line of Credit
Margin over basis of interest rate (as a percent)			2.18%
Line of Credit
Line of Credit
Maximum borrowings				$ 25,000,000
Term of debt				3 years
Amount of refinancing costs											128,000
Number of properties in which borrowing amount collateralized | item				23
Line of Credit | Woodland Park Apartments LLC Newton Massachusetts
Line of Credit
Payment on line of credit											8,000,000
Credit line balance											17,000,000
Funds drawn by the company											$ 25,000,000
Line of Credit | Webster Green Apartments
Line of Credit
Payment on line of credit	$ 16,000,000	$ 8,000,000			$ 4,000,000
Credit line balance							$ 5,000,000		$ 5,000,000
Line of Credit | Webster Green Apartments | Subsequent event
Line of Credit
Loan amount													$ 2,000,000
Line of Credit | Federal Funds Rate
Line of Credit
Basis of effective interest rate used in calculation of Base Rate (as a percent)				0.50%
Line of Credit | LIBOR
Line of Credit
Basis of effective interest rate used in calculation of Base Rate (as a percent)				1.00%
Margin over basis of interest rate (as a percent)				2.50%
Line of Credit | Minimum
Line of Credit
Pledged interests of the Partnership's ownership interest (as a percent)				49.00%
Commitment fee for unused amount (as a percent)				0.15%
Line of Credit | Maximum
Line of Credit
Pledged interests of the Partnership's ownership interest (as a percent)				100.00%
Commitment fee for unused amount (as a percent)				0.20%