The amount of the costs of construction or maintenance of any system of improvement assessed against any city, town or county may be met by levies to be paid in similar installments and extending over a like period of time as the assessments against property benefited are spread, or such amounts may be met by the issue and sale of the bonds of such city, town or county in the manner in which bonds to meet general indebtedness of such city, town or county are issued. The proper authorities of such city, town or county shall make the necessary levies to meet such amounts thus apportioned thereto as a general levy on all property therein.