The hospital district shall charge sufficient rentals or rates for services rendered by the parking station to produce revenues sufficient to:

1. (1) pay all expenses of owning, operating, and maintaining the parking station;
2. (2) pay the principal of and interest on the bonds when due; and
3. (3) create and maintain a bond reserve fund and other funds as provided by the bond order or trust indenture.

Acts 1989, 71st Leg., ch. 678, Sec. 1, eff. Sept. 1, 1989.