The authority is authorized to issue bonds from time to time in its discretion for the purpose of paying all or any part of the cost of acquiring, purchasing, constructing, reconstructing, improving or extending any project and acquiring necessary land and equipment therefor. The authority may issue such types of bonds as it may determine, including (without limiting the generality of the foregoing) bonds payable as to principal and interest: (i) from its revenues generally; (ii) exclusively from the income and revenues of a particular project; or (iii) exclusively from the income and revenues of certain designated projects, whether or not they are financed in whole or in part from the proceeds of such bonds. Any such bonds may be additionally secured by a pledge of any grant or contribution from a participating locality, the Commonwealth or any political subdivision, agency or instrumentality thereof, any federal agency or any unit, private corporation, copartnership, association, or individual, or a pledge of any income or revenues of the authority, or a mortgage on any project or other property of the authority, or any contract obligation or undertaking, whether in the nature of a guaranty or otherwise, of any participating locality. However, any such contract obligation or undertaking by any participating locality which is a city or town shall not be considered an indebtedness within the meaning of any debt limitation or restriction and that any such contract obligation or undertaking by a participating locality which is a county shall be authorized in accordance with the provisions of Article VII, Section 10 (b) of the Constitution of Virginia. Neither the members of the board of the authority nor any person executing the bonds shall be liable personally on the bonds by reason of the issuance thereof. The bonds and other obligations of the authority (and such bonds and obligations shall so state on their face) shall not be a debt of the Commonwealth or any political subdivision thereof other than the participating localities which have entered into contract obligations or other undertakings with respect to the repayment thereof as authorized in the preceding paragraph, and neither the Commonwealth nor any political subdivision thereof other than the authority and, to the extent provided in the preceding paragraph, participating localities, shall be liable thereon, nor shall such bonds or obligations be payable out of any funds or properties other than those of the authority and those created by contract obligations or undertakings of any participating localities entered into pursuant to the preceding paragraph. The bonds shall not constitute an indebtedness within the meaning of any debt limitation or restriction. Bonds of the authority are declared to be issued for an essential public and governmental purpose.