SUBSEQUENT EVENTS - Narrative (Details)																	1 Months Ended				12 Months Ended		31 Months Ended	43 Months Ended
	Mar. 31, 2021 USD ($)	Mar. 29, 2021 USD ($)	Mar. 25, 2021 USD ($) $ / shares	Mar. 05, 2021 USD ($)	Mar. 01, 2021 USD ($)	Feb. 25, 2021 USD ($) $ / shares	Feb. 12, 2021 USD ($)	Feb. 01, 2021 USD ($) $ / shares shares	Jan. 31, 2021 USD ($) $ / shares	Jan. 29, 2021 USD ($) shares	Jan. 25, 2021 $ / shares shares	Jan. 22, 2021 USD ($) $ / shares	Jan. 21, 2021 USD ($)	Jan. 07, 2021 USD ($)	Aug. 13, 2020 USD ($)	Dec. 19, 2019 USD ($)	Feb. 28, 2021 USD ($)	Jan. 31, 2021 USD ($) $ / shares	Jan. 27, 2021 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares	Dec. 31, 2020 USD ($) $ / shares	Dec. 31, 2019 USD ($) $ / shares	Feb. 28, 2021 USD ($) shares	Feb. 28, 2021 USD ($) shares	Mar. 24, 2021 USD ($) $ / shares shares	May 20, 2020 $ / shares	Dec. 23, 2019 USD ($)	Jan. 14, 2019 $ / shares	Jan. 18, 2018 $ / shares	Jul. 20, 2016 USD ($)	Jul. 15, 2015 USD ($)
Subsequent Event [Line Items]
Proceeds from issuance of common stock and investor deposits																					$ 10,908,856	$ 34,555,691
Dividends																				$ 705,596	$ 11,701,828	10,585,519
Net asset value (in usd per share) | $ / shares																				$ 21.01	$ 21.01					$ 21.01			$ 30.00
Repurchases of common stock																					$ 17,576,261	12,145,903
Disposal group, including discontinued operation, consideration																				$ 31,096,403	31,096,403
Proceeds from sale of real estate investments																						0
Repayments of unsecured credit facility																					$ 6,000,000	$ 13,869,000
Unsecured Credit Facility | Unsecured Debt
Subsequent Event [Line Items]
Maximum borrowing capacity																$ 12,000,000
Repayments of unsecured credit facility															$ 6,000,000
Unsecured Credit Facility | Unsecured Debt | Prime Rate
Subsequent Event [Line Items]
Basis spread on variable rate ( as a percent)																1.00%
Unsecured Credit Facility | Unsecured Debt | Loans, Mature on October 15, 2021
Subsequent Event [Line Items]
Maximum borrowing capacity															$ 6,000,000
DRP
Subsequent Event [Line Items]
Net asset value (in usd per share) | $ / shares																												$ 30.48
Minimum | Unsecured Credit Facility | Unsecured Debt
Subsequent Event [Line Items]
Line of credit facility, interest rate during period																5.50%
IPO
Subsequent Event [Line Items]
Common stock subscriptions																															$ 30,000,000
Class C
Subsequent Event [Line Items]
Stock split, conversion ratio																						1
Common stock (in usd per share) | $ / shares																				$ 0.001	$ 0.001	$ 0.001
Common stock subscriptions																											$ 800,000,000
Minimum share value																														$ 500
Class C | DRP
Subsequent Event [Line Items]
Common stock subscriptions																											75,000,000
Class C | Follow-on Offering
Subsequent Event [Line Items]
Common stock subscriptions																											$ 725,000,000
Class S
Subsequent Event [Line Items]
Common stock (in usd per share) | $ / shares																				$ 0.001	$ 0.001	$ 0.001
Subsequent Event
Subsequent Event [Line Items]
Stock split, conversion ratio								0.3333
Dividends																	$ 620,788	$ 695,768
Distributions declared per share per day (in usd per share) | $ / shares			$ 0.00287670			$ 0.00287670						$ 0.00287670
Annualized distribution rate (in usd per share) | $ / shares			$ 1.05			$ 1.05						$ 1.05
Percentage of NAV per share			4.56%			5.00%						5.00%
Net asset value (in usd per share) | $ / shares			$ 23.03			$ 21.01		$ 23.03				$ 21.01							$ 23.03
Subsequent Event | Class R OP Units
Subsequent Event [Line Items]
Other ownership interests, conversion ratio											1
Other ownership interests, conversion ratio, diluted EPS threshold											0.4
Other ownership interests, diluted EPS threshold | $ / shares											$ 1.05
Other ownership interests, units outstanding (in shares) | shares								360,000
Subsequent Event | Class R OP Units | Mr. Halfacre
Subsequent Event [Line Items]
Other ownership interests, units issued (in shares) | shares											120,000
Other ownership interests, units issued, period											3 years
Other ownership interests, units outstanding (in shares) | shares								210,667
Subsequent Event | Class R OP Units | Mr. Pacini
Subsequent Event [Line Items]
Other ownership interests, units issued (in shares) | shares											100,000
Other ownership interests, units issued, period											3 years
Other ownership interests, units outstanding (in shares) | shares								33,333
Subsequent Event | Class R OP Units | Employees of Company
Subsequent Event [Line Items]
Other ownership interests, units issued (in shares) | shares											348,000
Other ownership interests, units outstanding (in shares) | shares								116,000
Subsequent Event | Class R OP Units, Future Compensation | Mr. Halfacre
Subsequent Event [Line Items]
Other ownership interests, units issued (in shares) | shares											512,000
Subsequent Event | Credit Facility | New Credit Facility
Subsequent Event [Line Items]
Maximum borrowing capacity		$ 22,000,000
Amount borrowed under the credit facility	$ 6,000,000
Line of credit facility, interest rate during period		4.75%
Debt origination fees paid		$ 77,000
Line of credit facility, unused commitment fee percentage		0.15%
Minimum debt service coverage ratio		125.00%
Minimum tangible NAV		$ 120,000,000
Subsequent Event | Credit Facility | New Credit Facility | Prime Rate
Subsequent Event [Line Items]
Basis spread on variable rate ( as a percent)		1.00%
Subsequent Event | Credit Facility | Revolving Line of Credit Due by September 30, 2021
Subsequent Event [Line Items]
Repayments of unsecured credit facility		$ 6,000,000
Subsequent Event | DRP
Subsequent Event [Line Items]
Dividends			$ 352,525			$ 386,841						$ 391,866
Subsequent Event | GSA (MSHA) | Swap
Subsequent Event [Line Items]
Derivative, cost of hedge net of cash received				$ 9,900
Subsequent Event | Retail | Dollar General, Castalia and Lakeside
Subsequent Event [Line Items]
Operating lease, lease incentives, free rent period													1 month
Subsequent Event | Retail | Dollar General, Lakeside
Subsequent Event [Line Items]
Operating lease minimum annual rents													$ 6,753
Subsequent Event | Retail | Dollar General, Castalia
Subsequent Event [Line Items]
Operating lease minimum annual rents													$ 6,610
Subsequent Event | Retail | Chevron Gas Station, Roseville
Subsequent Event [Line Items]
Disposal group, including discontinued operation, consideration														$ 4,050,000
Proceeds from sale of real estate investments														$ 3,914,909
Subsequent Event | Retail | EcoThrift
Subsequent Event [Line Items]
Disposal group, including discontinued operation, consideration										$ 5,375,300
Proceeds from sale of real estate investments										$ 2,684,225
Subsequent Event | Retail | Chevron Gas Station, San Jose
Subsequent Event [Line Items]
Disposal group, including discontinued operation, consideration							$ 4,288,888
Proceeds from sale of real estate investments							$ 4,055,657
Subsequent Event | Office | Northrop Grumman
Subsequent Event [Line Items]
Tenant improvements for operating lease extension					$ 1,150,000
Subsequent Event | IPO and Over-Allotment Option | MACS
Subsequent Event [Line Items]
Expected consideration to be raised																									$ 115,000,000
Subsequent Event | IPO | MACS
Subsequent Event [Line Items]
Expected consideration to be raised																									100,000,000
Escrow deposited for MACS																									$ 4,500,000
Warrants expected to be purchased (in shares) | shares																									9,000,000
Number of securities to be purchased by each warrant (in shares) | shares																									0.5
Warrants exercise price (in usd per share) | $ / shares																									$ 11.50
Subsequent Event | Tenant Brokers | Office | Northrop Grumman
Subsequent Event [Line Items]
Leasing commission paid					128,538
Subsequent Event | Northrop Grumman | Office | Northrop Grumman
Subsequent Event [Line Items]
Leasing commission paid					$ 128,538
Subsequent Event | MVF | IPO and Over-Allotment Option | MACS
Subsequent Event [Line Items]
Common stock issued in transaction (in shares) | shares										2,875,000
Amount of stock offerings										$ 25,000
Subsequent Event | MVF | Over-Allotment Option | MACS
Subsequent Event [Line Items]
Common stock issued in transaction (in shares) | shares										375,000
Subsequent Event | MVF | IPO | MACS
Subsequent Event [Line Items]
Ownership percentage after stock offerings										20.00%
Subsequent Event | Class C
Subsequent Event [Line Items]
Common stock (in usd per share) | $ / shares								$ 0.001	$ 0.003									$ 0.003
Common stock issued in transaction (in shares) | shares																							6,748,695
Proceeds from issuance of common stock and investor deposits																							$ 199,861,618
Repurchases of common stock (in shares) | shares																			481,939
Repurchases of common stock																			$ 10,375,064
Share repurchase program, minimum holding period								6 months	90 days
Percentage of NAV, shares held for less than two years								98.00%
Percentage of NAV shares held for at least two years								100.00%
Percentage of NAV, shares held for less than one year									97.00%									97.00%
Percentage of NAV, shares held for one to two years									98.00%									98.00%
Percentage of NAV, shares held for two to three years									99.00%									99.00%
Percentage of NAV, shares held for at least three years									100.00%									100.00%
Minimum share value								$ 1,000	$ 500									$ 500
Subsequent Event | Class C | DRP
Subsequent Event [Line Items]
Common stock issued in transaction (in shares) | shares																							817,355
Proceeds from issuance of common stock and investor deposits																							$ 23,093,575
Share repurchase program, minimum holding period								6 months	90 days
Subsequent Event | Class C | Follow-on Offering
Subsequent Event [Line Items]
Common stock subscriptions																			$ 600,547,672
Subsequent Event | Class C | 2021 DRP Offering
Subsequent Event [Line Items]
Common stock subscriptions												$ 100,000,000
Subsequent Event | Class S
Subsequent Event [Line Items]
Common stock (in usd per share) | $ / shares								$ 0.001	$ 0.003									$ 0.003
Common stock issued in transaction (in shares) | shares																								63,876
Proceeds from issuance of common stock and investor deposits																								$ 1,935,770
Repurchases of common stock (in shares) | shares																			0
Minimum share value								$ 1,000	$ 500									$ 500
Subsequent Event | Class S | DRP
Subsequent Event [Line Items]
Common stock issued in transaction (in shares) | shares																								2,172
Proceeds from issuance of common stock and investor deposits																								$ 58,606