In order to defray the costs and expenses of the improvements authorized by sections 18-2001 and 18-2002, the mayor and council or chairman and board of trustees, as the case may be, may levy and collect special taxes and assessments upon the lots and parcels of real estate adjacent to or abutting upon the portion of the street or alley thus improved, or which may be specially benefited by such improvements, notwithstanding that the same may be unplatted and not subdivided; and the method of levying, equalizing, and collecting such special assessments, and generally financing such improvements by bond issues and other means, shall be as provided by law for paving and street improvements in such municipality. For the purpose of paying the cost of street improvements as provided in section 18-2001 the mayor and council or chairman and board of trustees, as the case may be, shall have the power, after the improvements have been completed and accepted, to issue negotiable bonds of such city or village to be called Paving Bonds, payable in not exceeding fifteen years and bearing interest payable annually or semiannually, which may be sold by the city for not less than the par value thereof. For the purpose of making partial payments as the work progresses, warrants bearing interest may be issued by the governing body of the city or village upon certificates of the engineer in charge showing the amount of work completed and materials necessarily purchased and delivered for the orderly and proper continuation of the project, in a sum not exceeding ninety-five percent of the cost thereof until the work has been completed and accepted by the city or village, at which time a warrant for the balance of the amount may be issued, which warrants shall be redeemed and paid upon the sale of the bonds or from any other funds available. The city or village shall pay to the contractor interest at the rate of eight percent per annum on the amounts due on partial and final payments beginning forty-five days after the certification of the amounts due by the engineer in charge and approval by the governing body, and running until the date that the warrant is tendered to the contractor. All special assessments which may be levied upon property specially benefited by such work or improvements shall, when collected, be set aside and constitute a sinking fund for the payment of the interest and principal of such bonds. There shall be levied annually upon all taxable property in such city or village a tax which, together with such sinking fund derived from special assessments, shall be sufficient to meet payments of interest and principal as the same become due.