The area proposed for a mobile home park shall have at least seven acres of gross development area or provide for a minimum of 40 single wide mobile home lots or a combination of single and double wide with a minimum square footage for single wide of 6,000 square feet and double wide of 7,200 square feet. Such area may be developed in two or more stages, provided that said stages conform in all respects with the overall mobile home park development plan. Occupancy shall not be permitted until all facilities and improvements are installed and operational for not less than 25 mobile home lots. The maximum density allowed for the gross development area shall be six mobile home units per acre. No mobile home shall be connected to water, sewer, or electrical service unless the mobile home complies with the standards and requirements prescribed by Standard for Mobile Homes, USAS A119.1, 1963 and amendments thereto published by United States of America Standards Institute as applicable or an equivalent standard. Compliance with the aforesaid standard shall be determined by the Building Official. A certificate issued by the manufacturer of the mobile home shall be permanently affixed on a readily visible location on the exterior of the mobile home as prima facie evidence of such compliance.