In cases where a builder or developer desires to install sewers, laterals and building sewers to every housing unit within a housing development prior to their individual sale, he shall meet all conditions as set forth in this section and in other sections of these rates, rules and regulations. Plot plans for such a development must be submitted to the borough for approval prior to any construction. Sewer plans conforming to all original specifications established by the borough as to type of pipe, location of mains, size of pipe, grades, methods of laying pipe and the type and construction of all necessary appurtenances must be prepared, approved by the borough and approval obtained from the necessary state agencies. The engineering fees and charges for permits will be paid by the builder or developer. In no case will lesser standards than exist in the sewer system presently to be constructed and as outlined in these rates, rules and regulations be permitted for any future extensions. Upon approval of such plans by the borough, the extensions may be constructed by and at the expense of the builder or developer, but only under the inspection of an inspector designated by the borough. The cost of such inspection, including salaries and expenses, shall be borne by the builder or developer making the extensions.