(a) To pay the costs of a project, the county may issue bonds payable from and secured by a pledge of the net revenue of the project. The cost of a project may include:
(1) legal, fiscal, and engineering expenses; and
(2) interest during the construction of the project.
(b) If provided in the order issuing a bond, bonds issued under Subsection (a) may be additionally secured by an ad valorem tax imposed under § 9, Article VIII, Texas Constitution. If the county places any part of the ad valorem tax in a permanent improvement fund, only the ad valorem taxes in that fund may be used as the additional security.

(c) Before a county may issue bonds under Subsection (a) to pay for a project, the bonds must be approved in an election held under § 1477.057. If an ad valorem tax is to be imposed under Subsection (b) to secure bonds, the tax must also be approved at the election held to approve the issuance of the bonds.