That none of the funds derived from the sale of bonds issued under the provisions of this act N.M. Stat. Ann. § 6-13-1 to 6-13-26, except so much thereof as shall be necessary to defray the costs of the issuance of such bonds and the accrued interest from the date thereof to the time of delivery, shall ever be used or expended for any purpose other than those for which the authority to issue the same by this act is given.