(7A) Whenever a lessor who receives rent in advance for the last month of tenancy transfers his interest in the dwelling unit for which the rental advance was received, whether by sale, assignment, death, appointment of a receiver or trustee in bankruptcy, or otherwise, the lessor shall credit an amount equal to such rental advance together with any interest which has accrued thereon for the benefit of the tenant who made such rental advance, to the successor in interest of such lessor, and said successor in interest shall be liable for crediting the tenant with such rental advance, and for paying all interest accrued thereon in accordance with the provisions of this section from the date upon which said transfer is made; provided, however, that the granting of a mortgage on such premises shall not be deemed a transfer of interest. The successor in interest shall, within forty-five days from the date of said transfer, notify the tenant who made such rental advance that such rental advance was so credited, and that such successor has assumed responsibility therefor pursuant to the foregoing provision. Such notice shall also contain the lessor's name, business address, and business telephone number, and the name, business address, and business telephone number of his agent, if any. Said notice shall be in writing.