If more than two-thirds of the votes cast at the election are in favor of incurring the indebtedness, the board may by resolution at any time it deems proper provide for the form and execution of the bonds, and for the issuance of any part thereof, and may sell or dispose of the bonds so issued at such times or in such manner either for cash in lawful money of the United States, or its equivalent as it may deem to be to the public interest.