(14) where the amount of rent charged to and paid by the tenant is less than the legal regulated rent for the housing accommodation, the amount of rent for such housing accommodation which may be charged upon vacancy thereof, may, at the option of the owner, be based upon such previously established legal regulated rent, as adjusted by the most recent applicable guidelines increases and any other increases authorized by law. For any tenant who is subject to a lease on or after the effective date of a chapter of the laws of two thousand nineteen which amended this paragraph, or is or was entitled to receive a renewal or vacancy lease on or after such date, upon renewal of such lease, the amount of rent for such housing accommodation that may be charged and paid shall be no more than the rent charged to and paid by the tenant prior to that renewal, as adjusted by the most recent applicable guidelines increases and any other increases authorized by law. Provided, however, that for buildings that are subject to this statute by virtue of a regulatory agreement with a local government agency and which buildings receive federal project based rental assistance administered by the United States department of housing and urban development or a state or local section eight administering agency, where the rent set by the federal, state or local governmental agency is less than the legal regulated rent for the housing accommodation, the amount of rent for such housing accommodation which may be charged with the approval of such federal, state or local governmental agency upon renewal or upon vacancy thereof, may be based upon such previously established legal regulated rent, as adjusted by the most recent applicable guidelines increases and other increases authorized by law; and