Ariz. Rev. Stat. § 48-148 – Charges for payment of undertaking

A. The board of directors of the district issuing the bonds shall prescribe charges and revise them whenever necessary so that any undertaking for which the bonds were issued shall always remain self-supporting with revenue sufficient:
1. 1. To pay when due all bonds and interest thereon, for the payment of which the revenue has been pledged, encumbered or charged.
2. 2. To provide for all expenses of operation, maintenance, expansion and replacement of facilities.
3. 3. To provide reasonable reserves for such purposes.
B. Until the payment of all bonds on an undertaking issued under this article, neither the receipts nor expenditures in connection with the operation of the undertaking shall be included in any budget of the district, and the actual expenditures from the funds, other than for bond interest and redemption, shall be deemed to have been included in and to have constituted a part of the budget adopted by the district for the fiscal year in which the bonds were so paid.