; and (II) pledge any grant or allocation for which the issuer is or may become eligible under this subsection or subsection (e) for the repayment of notes or other obligations so guaranteed. (ii) Crediting of grants The Secretary may, notwithstanding any other provision of this Act, apply grants pledged pursuant to clause (i)(II) of this subparagraph to any repayments due the United States as a result of such guarantees. (F) Full faith and credit The full faith and credit of the United States is pledged to the payment of all guarantees made under this paragraph. Any such guarantee made by the Secretary shall be conclusive evidence of the eligibility of the obligations for such guarantee with respect to principal and interest, and the validity of any such guarantee so made shall be incontestable in the hands of a holder of the guaranteed obligations. (G) Amount Subject only to the absence of qualified requests for guarantees and to the availability of amounts to cover the costs (as such term is defined in section 502 of the Federal Credit Reform Act of 1990 ( 2 U.S.C. 661a )), as are provided in advance in appropriation Acts, the Secretary shall enter into commitments to guarantee notes and obligations under this paragraph having an aggregate principal amount of $500,000,000 each for fiscal years 2018, 2019, and 2020. . (b) Requirements for properties with housing tax credits Section 9 of the United States Housing Act of 1937 ( 42 U.S.C. 1437g ) is amended by adding at the end the following new subsection: (p) Requirements for properties with housing tax credits A public housing agency that utilizes tax credits under section 42 of the Internal Revenue Code of 1986 for rental housing units that are currently or formerly assisted under subsection (d) or (e) shall ensure, with respect to such units, that— (1) all significant tenant and applicants rights are continued and enforceable