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Represents the amortization period of value of the in-place leases.

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Represents the aggregate purchase price of real estate properties acquired by the entity.

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Represents the aggregate purchase price of real estate properties acquired by the entity allocated to tenant relationships.

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Represents the amortization period of value of the tenant relationships.

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Face (par) amount of debt instrument at time of issuance.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Period between issuance and maturity of long-term debt, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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The number of units in a real estate property owned as of the balance sheet date.

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Amount of cash outflow for cost from early extinguishment and prepayment of debt. Includes, but is not limited to, third-party cost, premium paid, and other fee paid to lender directly for debt extinguishment or debt prepayment. Excludes accrued interest.

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The cash outflow to repay long-term debt that is wholly or partially secured by collateral. Excludes repayments of tax exempt secured debt.

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MORTGAGE NOTES PAYABLE (Mortgage by property) (Details)					6 Months Ended
MORTGAGE NOTES PAYABLE (Mortgage by property) (Details)	Mar. 31, 2020 USD ($)	Dec. 21, 2019	Dec. 20, 2019 USD ($) item	May 31, 2019 USD ($)	Jun. 30, 2020 USD ($) property	Jun. 30, 2019 USD ($)	Aug. 31, 2014	Dec. 31, 2005	Mar. 07, 2005 item
MORTGAGE NOTES PAYABLE
Repayment of loan					$ 1,000,000	$ 2,000,000
Loan balance					$ 285,867,000
Residences at Captain Parkers LLC Residential Apartments Lexington, Massachusetts
MORTGAGE NOTES PAYABLE
Loan amount				$ 20,750,000
Interest rate (as a percent)				4.05%
Loan balance				$ 20,071,000
Mortgage prepayment penalties				$ 202,000
57 Mill Street
MORTGAGE NOTES PAYABLE
Number of units \| item			181
Loan amount			$ 31,000,000
Purchase price of real estate properties			59,550,000
Cash from reserves			10,550,000
Line of credit			18,000,000
Closing costs associated with financing			237,000
Purchase price allocated to the value of the in-place leases			1,282,000
Purchase price allocated to the value of the tenant relationships			$ 136,000
Amortization period of value of the in-place leases			12 months
Amortization period of value of the tenant relationships		36 months
Hamilton Essex 81
MORTGAGE NOTES PAYABLE
Number of units					49	49			48
Brookside Associates LLC Residential Apartments Woburn, Massachusetts
MORTGAGE NOTES PAYABLE
Loan amount	$ 6,175,000
Repayment of loan	2,390,000
Closing Costs	$ 136,000
Interest rate (as a percent)	3.53%
Initial Advance \| 57 Mill Street
MORTGAGE NOTES PAYABLE
Loan amount			$ 31,000,000
Interest rate (as a percent)		3.586%
Subsequent Advance \| 57 Mill Street
MORTGAGE NOTES PAYABLE
Loan amount			4,000,000
Interest rate (as a percent)		3.50%
Minimum \| 57 Mill Street
MORTGAGE NOTES PAYABLE
Loan amount			35,000,000
Maximum
MORTGAGE NOTES PAYABLE
Loan amount			$ 35,000,000
Mortgages payable \| Hamilton on Main Apartments, LLC
MORTGAGE NOTES PAYABLE
Interest rate (as a percent)							4.34%	5.18%
Amortization period of debt								30 years
Debt Instrument, Amortization Term								30 years
Mortgages payable \| Minimum
MORTGAGE NOTES PAYABLE
Interest rate (as a percent)					3.53%
Mortgages payable \| Maximum
MORTGAGE NOTES PAYABLE
Interest rate (as a percent)					5.66%