For the purpose of providing funds to pay the cost of any improvement made under the provisions of this article, the cost of which, in whole or in part, is proposed to be assessed against the property drained, served, and benefited by the improvements being provided, the authority may borrow money temporarily, executing its negotiable note therefor, which note may not run longer than a period of one year, or issue bonds. Such temporary note or issue of bonds may be made before the contract is let for the improvements or during the progress of the work, in installments as the work progresses, and the making of one loan or the issue of one series of bonds shall not exhaust the power of the authority to provide sufficient funds for the completion of the improvement. The authority may pledge as security for such loan, whether evidenced by notes or bonds, the proceeds of the assessments made or to be made against the property benefited by the improvement and may transfer and assign for the benefit of the holder of the said note or bond the lien of the authority thereon with power to enforce the same by civil action, but if notes or bonds shall be issued before the completion of the work, they shall not be issued in excess of the cost of the improvement as estimated at the time of the issue of the said notes or bonds. If money is borrowed and notes or bonds issued after the work is completed, such notes or bonds shall not exceed in the aggregate the total cost of the improvement. No irregularity or technical defect in the proceedings relating to the making of the improvement shall in any way affect the power of the authority to borrow money for the completion of the improvement.