(a) Bonds issued under this subchapter must be payable from and secured by a pledge of:
(1) the net revenue of the parking facility; and
(2) any other revenue incident to the ownership of the parking facility, including money received from a lease of the facility.
(b) The commissioners court may also provide for the bonds to be payable from and secured by the imposition of an ad valorem tax. The tax may not exceed two and one-half cents on each $100 valuation of taxable property in the county.