Strategy and Investment in Rural Housing Preservation Act of 2021 This bill provides assistance to rural, multifamily rental-housing projects and tenants. Specifically, the Department of Agriculture (USDA) must implement a program for the preservation and revitalization of such housing projects that are financed with USDA loans. As part of this program, USDA may restructure existing housing loans by reducing or eliminating interest and deferring loan payments. When offering to restructure such a loan, USDA must also offer to renew a property owner's contract for rental assistance payments for a term of 20 years, provided that the property owner agrees to maintain the property as decent, safe, and sanitary housing for the full term of the contract. USDA must annually provide written notice explaining the options to restructure such loans to certain property owners. Additionally, USDA may provide technical assistance grants to qualified nonprofit organizations and public housing agencies to help borrowers acquire multifamily rental-housing properties in areas where there is a risk of loss of affordable housing. Further, USDA may provide rural housing vouchers for low-income households (including those not receiving rental assistance) residing in certain properties financed with or insured by USDA loans. The bill also extends existing housing protections for victims of domestic violence, dating violence, sexual assault, and stalking to victims who receive rural housing voucher assistance. These protections include protections against denial or termination of assistance or eviction.