The revenue derived from rates, fares, and charges fixed under subdivision (19) of section 18-812, from property taxes levied pursuant to section 18-822, from any grants or loans received under subdivision (17) of section 18-812, and from any donations or other funds received from other sources shall at all times be sufficient in the aggregate to provide for the payment of (1) all operating costs of the regional metropolitan transit authority, (2) interest on the principal of all revenue bonds, revenue certificates, equipment trust notes or certificates, and other obligations of the authority, and all other charges upon such revenue as may be provided by any trust agreement executed by such authority in connection with the issuance of revenue bonds or certificates under the Regional Metropolitan Transit Authority Act, and (3) any other costs and charges, acquisitions, installations, replacements, or reconstruction of equipment, structures, or rights-of-way not financed through the issuance of revenue bonds or certificates.