As soon as any contract is let pursuant to section 14-534, the city council of a city of the metropolitan class is authorized to issue bonds of the city in amounts sufficient to pay for the total work to be done under such contract. Unless bonds are issued for such purpose, the contract shall not be performed and shall not be binding upon the city. Bonds issued under the provisions of section 14-534 shall be denominated grading bonds, and shall state upon the face of such bonds the street or part of street to be graded from the proceeds of such bonds. Such bonds shall be due and payable in five years from date of such bonds, shall draw interest at a rate not to exceed the rate of interest specified in section 45-104.01, as such rate may from time to time be adjusted by the Legislature, payable semiannually, shall have interest coupons attached, and shall not be sold or disposed of below par. The proceeds from such bonds shall be used only for the purpose of paying the costs of the grading for which issued. Such bonds may be sold or disposed of in the manner deemed best or advisable. As the work of grading progresses, partial estimates may be allowed and paid and the final estimates paid as soon as allowed.