For the purpose of raising funds for the payment of interest on and principal of such bonds and for the maintenance and repairs of said lateral sewers, the board of trustees shall have the power to impose and collect an annual rental charge from the owners of all real estate abutting said lateral sewers, including the owners of public property devoted to public use. The annual rental charge shall be apportioned according to the assessed valuation of each tract and parcel of such property, and the assessor of the county shall separately assess that portion of such tracts and parcels of property as lie within such subdistrict, and he shall also assess and enter upon the records of his office the assessed valuation of all such property in such subdistrict, including school property, public or private, whether or not such property is otherwise exempt from taxation. The total amount of annual rental charges to be imposed shall not exceed the estimated amount necessary to be imposed to provide funds sufficient to pay the interest on and the principal of such bonds, plus the estimated cost of maintenance as fixed by the board of trustees. Such rental charges may be imposed or collected in semiannual or quarterly installments as the board of trustees may direct, and shall be a lien upon such property from the date they are imposed by the board of trustees.