From the date of service of the notice under RCW 59.28.040 until either twelve months have elapsed or expiration or prepayment of the rental assistance contract, mortgage, or loan, whichever is later, no owner of federally assisted housing may increase the rent of a federally assisted housing unit, or the share of the rent paid by the tenant, above the amount authorized by the federal assistance program applicable to the project prior to expiration or prepayment of the rental assistance contract or mortgage or loan.