Housing is a Human Right Act of 2021 This bill establishes and expands programs to assist homeless and housing-unstable individuals and establishes new real property-related taxes to fund specified Department of Housing and Urban Development (HUD) programs. HUD must establish the Community Development Block Grant Plus Program for state and local governments to assist homeless and housing-unstable individuals as well as cost-burdened households. These funds may be used only for certain activities that assist these populations, including the construction of new affordable housing. The bill also establishes other grant programs to assist these individuals, such as by facilitating access to voting and libraries. Governmental entities may not receive assistance under the bill unless they have, or are working to implement, policies that (1) do not criminally punish homeless individuals for sleeping outside or on public property, and (2) comply with constitutional protections for these individuals' property. In addition, the bill establishes taxes on (1) the sale or exchange of real property of at least $10 million, (2) the sale or exchange of real property involving an anonymous entity, and (3) rent received by landlords that own large amounts of dwelling units. The revenue from these taxes must be credited to various HUD programs in specified percentages. The Government Accountability Office must study (1) the allocation formula for Emergency Food and Shelter grants, (2) recipient compliance with various grant program guidelines, and (3) barriers related to access to essential documents that homeless and housing-unstable individuals face.