Not less than thirty days after an election in which a majority of the legal votes cast shall be in favor of the proposed annual levy of taxes the governing body of the county may issue negotiable coupon bonds of the county in an amount not exceeding the approximate cost of the proposed paving as determined by the governing body of the county as hereinabove provided. Such bonds may be issued either as a single issue or from time to time in separate issues as the governing body of the county may determine to be advisable.