Municipalities may issue mortgage bonds beyond the general limits of the bonded indebtedness prescribed by law for the purpose of defraying the cost, or a part thereof, of a sewage disposal plant and system or of a garbage disposal plant in accordance with the provisions of section 40-34-02. The bonds shall not impose any general liability upon the issuing municipality but shall be paid only out of the revenues received from the service charges as provided in this chapter or from the sale of the property under foreclosure of the mortgage or deed of trust. The bonds shall be sold for not less than ninety-eight percent of par and shall bear interest at a rate or rates resulting in an average annual net interest cost of not more than twelve percent per annum on those issues which are sold at private sale. There is no interest rate ceiling on those issues sold at public sale or to the state of North Dakota or any of its agencies or instrumentalities. No bonds shall be issued, however, except upon the affirmative vote of three-fifths or more of the members of the governing body of the issuing municipality, and the form, recitals, maturities, rate of interest, and whether the bonds shall be payable annually or semiannually, shall be determined by the same vote. A municipality is authorized to execute and deliver any mortgage or deed of trust contemplated under this chapter.