In order to produce an amount sufficient to meet the interest on the revenue bonds, and other expenses, payable prior to the completion of the sewage works, after the contract for construction of the sewer system has been let and actual work commenced thereunder, the owners of each and every lot, parcel of real estate, or building to be connected with the Town's sanitary sewage system as a result of construction of the sewage works, shall pay, each month, fifty (50) percent of the rates and charges established above, for each such building to be connected. Beginning with the first month after the sanitary sewers are available for connection and use to any lot, parcel of real estate or building, the full rates and charges shall become effective for such lot, parcel of real estate or building; but in any event, the full rates and charges shall become effective no later than July 1, 1982, so that billings for full rates and charges shall be rendered no later than August 1, 1982, provided, however, that this section shall not apply to any vacant land unless a building permit for construction has been issued thereon.