(5) The principal of and interest upon the bonds shall be payable, except as provided in this act, solely from the revenue derived from the operation of the housing project or combined projects, for the purchase, acquisition, construction, improvement, enlargement, extension, or repair of which the bonds are issued, and from contributions received for or in aid of the project or combined projects, from whatever source derived. The contributions may be pledged to the payment of any or all bonds issued in connection with the project or combined projects, as the borrower may provide. Bonds issued pursuant to this act shall not constitute an indebtedness of a borrower within the meaning of state constitutional provisions or statutory limitations. There shall be plainly stated on the face of each bond substantially as follows: "This bond is a revenue bond and the principal of and interest on this bond are exempt from any and all state, county, city, village, or other taxation under the laws of this state and are secured by the statutory lien created by 1933 (Ex Sess) PA 18, MCL 125.651 to 125.709c, and payable solely from contributions received for or in aid of the project or combined projects in connection with which the bonds are issued or from the revenues of the project or combined projects or from both the revenues and contributions, as the case may be, and are not a general obligation of the borrower."