If the resolution adopted by the county board or by petition, provides for the issuance of revenue bonds or other evidence of indebtedness, the retirement of the principal thereof and the interest thereon, to be accomplished from sources other than direct county taxes, the county board shall issue and sell such amounts of such bonds or other evidences of indebtedness as the Commission shall determine and certify, from time to time as being necessary to provide the means for accomplishing the purposes for which such bonds or other evidences of indebtedness are to be issued as set forth in said resolution. Such bonds or other evidence of indebtedness shall be issued in conformity to the requirements and provisions of the said resolution authorizing such issuance. The principal of such bonds or other evidences of indebtedness shall be discharged within thirty years after the date of the adoption of said resolution. Such bonds or other evidences of indebtedness shall bear interest, payable semi-annually, at a rate not to exceed that permitted in “An Act to authorize public corporations to issue bonds, other evidences of indebtedness and tax anticipation warrants subject to interest rate limitations set forth therein”, approved May 26, 1970, as now or hereafter amended. The proceeds from the sale of each issue of bonds shall be deposited in the county treasury and identified as “County Airports Revenue Bond Fund No. …..” Such proceeds shall be used only for the purposes stated in the said resolution and as specified in the certificate of the Commission as in this section provided. All such revenue bonds and other evidences of indebtedness shall not, in any event, constitute or be deemed an indebtedness of the county within the meaning of any constitutional provisions or statutory limitations as to debt, and it shall be so stated plainly on the face of each such bond or other evidence of indebtedness.