All bonds issued by a county under authority of this article shall be limited obligations of the county, the principal of and interest on which shall be payable solely out of the revenues derived from the leasing of the project to finance which the bonds are issued. Bonds and interest coupons issued under authority of this article shall never constitute an indebtedness of the county within the meaning of any state constitutional provision or statutory limitation and shall never constitute nor give rise to a pecuniary liability of the county or a charge against its general credit or taxing powers, and such fact shall be plainly stated on the face of each such bond. Such bonds may be executed and delivered at any time and from time to time, may be in such form and denominations, may be of such tenor, may be in registered or bearer form either as to principal or interest or both, may be payable in such installments and at such time or times not exceeding 30 years from their date, may be payable at such place or places, may bear interest at such rate or rates payable at such place or places and evidenced in such manner and may contain such provisions not inconsistent herewith, all as shall be provided in the proceedings of the county commission whereunder the bonds shall be authorized to be issued. The bonds issued under this article shall be subject to the general provisions of law, presently existing or that may hereafter be enacted, respecting the execution and delivery of the bonds of a county and respecting the retaining of options of redemption in proceedings authorizing the issuance of county securities. Such bonds shall not, however, be subject to the usury laws, and all such bonds are specifically exempted from the laws of the State of Alabama governing usury or prescribing or limiting interest rates, including, without limitation, the provisions of Chapter 8 of Title 8 of this Code. Any bonds issued under the authority of this article may be sold at public or private sale in such manner and from time to time as may be determined by the county commission to be most advantageous, and the county may pay all expenses, premiums and commissions which the county commission may deem necessary or advantageous in connection with the authorization, sale and issuance thereof. All bonds issued under the authority of this article and all interest coupons applicable thereto shall be construed to be negotiable instruments, despite the fact that they are payable solely from a specified source.