The following table summarizes certain information as of March 31, 2021 and December 31, 2020, with respect to the Company’s senior mortgage indebtedness (amounts in thousands):

Deferred financing costs

Costs incurred in obtaining long-term financing are amortized on a straight-line basis to interest expense over the terms of the related financing agreements, as applicable, which approximates the effective interest method.

Loss on Extinguishment of Debt and Debt Modification Costs

Upon repayment of or in conjunction with a material change (i.e. a 10% or greater difference in the cash flows between instruments) in the terms of an underlying debt agreement, the Company writes-off any unamortized deferred financing costs and fair market value adjustments related to the original debt that was extinguished. Prepayment penalties incurred on the early repayment of debt and costs incurred in a debt modification that are not capitalized are also included within loss on extinguishment of debt and debt modification costs on the consolidated statements of operations. Loss on extinguishment of debt and debt modification costs were $3.0 million and zero for the three months ended March 31, 2021 and 2020, respectively.

Master Credit Facility with Fannie Mae

On April 30, 2018, the Company, through certain subsidiaries of the Operating Partnership, entered into a Master Credit Facility Agreement (the “Fannie Facility”), which was issued through Fannie Mae’s Multifamily Delegated Underwriting and Servicing Program. The Fannie Facility includes certain restrictive covenants, including indebtedness, liens, investments, mergers and asset sales, and distributions. The Fannie Facility also contains events of default, including payment defaults, covenant defaults, bankruptcy events, and change of control events. Each note under the Fannie Facility is cross-defaulted and cross-collateralized and the Company has guaranteed the obligations under the Fannie Facility. As of March 31, 2021, the mortgage loans secured by ARIUM Metrowest, Falls at Forsyth and Outlook at Greystone were issued under the Fannie Facility.

On May 27, 2020, the Company, through certain subsidiaries of the Operating Partnership, entered into a $13.9 million floating rate advance (the “Fannie Facility Advance”) originated under the Fannie Facility and collateralized by the properties issued under the Fannie Facility. The Fannie Facility Advance matures on June 1, 2027 and bears interest at LIBOR plus 2.60%, subject to an interest rate cap,

with interest-only payments through June 2022 and then monthly payments based on thirty-year amortization. The Fannie Facility Advance may be prepaid without prepayment or yield maintenance beginning March 1, 2027.

On February 18, 2021, the Company, through certain subsidiaries of the Operating Partnership, entered into a $12.9 million floating rate advance originated under the Fannie Facility (the “Fannie Facility Second Advance”). Upon the sale of ARIUM Grandewood (refer to Note 3 for further information), the Company had the option to forgo the repayment of the principal balance and any related prepayment penalties and costs by substituting the collateral securing the senior mortgage with collateral of the same or higher value. As such, the Company elected to substitute the ARIUM Grandewood collateral on the Fannie Facility with its Falls at Forsyth property. As the collateral value of Falls at Forsyth exceeded the collateral value of ARIUM Grandewood, the Company elected to receive this incremental difference in collateral value as an advance under the Fannie Facility. The Fannie Facility Second Advance matures on March 1, 2028 and bears interest at the 30-day average SOFR plus 2.70%, subject to an interest rate cap, with interest-only payments through March 2023 and then monthly payments based on thirty-year amortization. The Fannie Facility Second Advance may be prepaid without prepayment or yield maintenance beginning December 1, 2027.

The Company may request future fixed rate advances or floating rate advances under the Fannie Facility either by borrowing against the value of the mortgaged properties (based on the valuation methodology established in the Fannie Facility) or adding eligible properties to the collateral pool, subject to customary conditions, including satisfaction of minimum debt service coverage and maximum loan-to-value tests. The proceeds of any future advances made under the Fannie Facility may be used, among other things, for general operating purposes and the acquisition and refinancing of additional properties to be identified in the future.

Debt maturities

As of March 31, 2021, contractual principal payments for the five subsequent years and thereafter are as follows (amounts in thousands):


Year	Total
2021 (April 1-December 31) ⁽¹⁾	$	81,986
2022		13,821
2023		126,023
2024		201,580
2025		369,102
Thereafter		672,843
	$	1,465,355
Add: Unamortized fair value debt adjustment		6,236
Subtract: Deferred financing costs, net		(10,840)
Total	$	1,460,751

(1)	$74.7 million represents a loan in connection with The District at Scottsdale. The loan has a June 2021 maturity date and contains two (2) three-month extension options, subject to certain conditions.

The net book value of real estate assets providing collateral for these above borrowings, including the Amended Senior Credit Facility, Second Amended Junior Credit Facility and Fannie Facility, was $1,971.2 million as of March 31, 2021.

The mortgage loans encumbering the Company’s properties are generally nonrecourse, subject to certain exceptions for which the Company would be liable for any resulting losses incurred by the lender. These exceptions vary from loan to loan but generally include fraud or a material misrepresentation, misstatement or omission by the borrower, intentional or grossly negligent conduct by the borrower that harms the property or results in a loss to the lender, filing of a bankruptcy petition by the borrower, either directly or indirectly, and certain environmental liabilities. In addition, upon the occurrence of certain events, such as fraud or filing of a bankruptcy petition by the borrower, the Company or our joint ventures would be liable for the entire outstanding balance of the loan, all interest accrued thereon and certain other costs, including penalties and expenses. The mortgage loans generally have a period where a prepayment fee or yield maintenance would be required.