The cost to any such sewer district of acquiring, constructing, improving or extending a sewerage system may be met:
(1) Through the expenditure by any such sewer district of any funds available for that purpose;
(2) Through the issuance of bonds for that purpose of the sewer district, payable from taxes to be levied and collected by such district;
(3) From any other funds which may be obtained under any law of the state or of the United States for that purpose; or
(4) From the proceeds of revenue bonds of such sewer district, payable solely from the revenues to be derived from the operation of such sewerage system or from any combination or all such methods of providing funds.