; and (2) exempt any multifamily residence or any attached or semi-attached residence that meets the requirements of any such alternative forms of mitigation from the requirements under subsection (b). (d) Water and energy efficiency Not less than 10 percent of all amounts made available pursuant to this section shall be used only for activities relating to water and energy efficiency and, at the discretion of the Administrator, other strategies to reduce emissions. 7. Housing Trust Fund (a) In general There is authorized to be appropriated for the Housing Trust Fund under section 1338 of the Housing and Urban Development Act of 1992 ( 12 U.S.C. 4568 ) $5,000,000,000, to remain available until expended. (b) Priority The Secretary shall ensure that priority for occupancy in dwelling units assisted with amounts made available pursuant to this section that become available for occupancy shall be given to persons and households who are homeless or at risk of homelessness. (c) Water and energy efficiency Not less than 10 percent of all amounts made available pursuant to this section shall be used only for activities relating to water and energy efficiency and, at the discretion of the Secretary, other strategies to reduce emissions. 8. Single-Family Housing Repair Loans and Grants (a) In general There is authorized to be appropriated for carrying out single family housing repair loans and grants under section 504 of the Housing Act of 1949 ( 42 U.S.C. 1474 ) $100,000,000, to remain available until expended. (b) Water and energy efficiency Not less than 10 percent of all amounts made available pursuant to this section shall be used only for activities relating to water and energy efficiency and, at the discretion of the Secretary of Agriculture, other strategies to reduce emissions. 9. Native American Housing Block Grant Program (a) In general There is authorized to be appropriated for carrying out the Native American housing block grant program under title I of the Native American Housing Assistance and