SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) - USD ($)		3 Months Ended		9 Months Ended	12 Months Ended
	May 31, 2021	Mar. 31, 2021	Jun. 30, 2020	Sep. 30, 2021	Dec. 31, 2020	May 05, 2021	May 03, 2021	Feb. 14, 2019	Jan. 15, 2019	Dec. 15, 2015
Debt and Equity Securities, FV-NI [Line Items]
Non-accrual status				$ 0
Recognized impairment				0
Allowance for loan losses				0
Principal amount				47,750,000	$ 40,250,000
Deferred financing costs amortized				$ 1,389,597
Common stock, shares authorized (in shares)				450,000,000	450,000,000
Common stock, par value (in dollars per share)				$ 0.01	$ 0.01
Common stock, shares issued (in shares)				24,947,883	24,943,383
Common stock, shares outstanding (in shares)				24,947,883	24,943,383
Stock repurchase program, authorized amount										$ 10,000,000
Preferred stock, shares authorized (in shares)				50,000,000	50,000,000
Preferred stock, par value (in dollars per share)				$ 0.01	$ 0.01
Preferred stock, shares issued (in shares)				2,400,000	0
Preferred stock, shares outstanding (in shares)				2,400,000	0
Preferred stock, dividend rate, percentage (as a percent)	7.875%	7.875%		7.875%
Other Operating Income (Expense)
Debt and Equity Securities, FV-NI [Line Items]
Reclassification of deferred financing costs from other assets to other operating expenses			$ 624,816
Series A Cumulative Redeemable Preferred Stock
Debt and Equity Securities, FV-NI [Line Items]
Preferred stock, shares authorized (in shares)				50,000,000	50,000,000		2,400,000
Preferred stock, par value (in dollars per share)				$ 0.01	$ 0.01
Preferred stock, shares issued (in shares)				2,400,000	0	2,400,000
Preferred stock, shares outstanding (in shares)				2,400,000	0
Delayed Draw Facility | Credit Agreement
Debt and Equity Securities, FV-NI [Line Items]
Principal amount				$ 47,750,000				$ 40,250,000	$ 40,250,000
Collateralized Loan Obligations
Debt and Equity Securities, FV-NI [Line Items]
Maximum exposure to loss from consolidated trusts				$ 166,250,000	$ 124,046,671