The agency may make grants to buyers of residential structures combined with first mortgage loans financed by the agency to be used in conjunction with the FHA Energy Efficient Mortgage Program, for the purpose of making repairs or improvements to increase energy efficiency in the home. Grants authorized by this section shall not be made with proceeds from the sale of bonds. Any such grant, and any costs directly associated with it, shall be funded through revenues realized by the agency from the grantee’s first mortgage loan, or securities backed by it, except that the agency may provide short-term interim funding of the grant to facilitate the transaction.