Notwithstanding any contrary provisions of this chapter, or any other general or special law or provision of any municipal charter, bonds issued by a city or town which are purchased by the United States of America, acting through the United States Department of Agriculture/Rural Development, or any successor agency or department, shall be payable either by maturity of principal in the case of serial bonds or by mandatory serial redemption in the case of term bonds, in annual installments of principal, the first installment not later than five (5) years and the last installment not later than forty (40) years after the date of the bonds.