No such assessment shall be so laid upon the abutting property owners until such improvements have been ordered pursuant to such ordinance upon the written consent, signed and filed with the city or town clerk, of not less than two thirds in number of the owners of the property abutting upon the street, sidewalk or part of either proposed to be improved and provision made for the payment by the corporate authorities of such city or town of not less than one half of the cost of such improvement. The times and terms of payment and rates of interest on deferred payments of assessments by such property owners shall be such as may be prescribed by ordinance.