Location of Dwellings and Buildings - Only one main building for single-family and two-family use, with permitted accessory buildings, may be located upon a lot or unplatted tract. Every means of access shall have a minimum width of twenty-five feet (25'). Where a lot is used for retail and dwelling purposes, more than one (1) main building may be located upon the lot, but only when such buildings conform to all the open space, parking and density requirements applicable to the uses and districts. Whenever two or more main buildings, or portions thereof, are placed upon a single lot or tract and such buildings do not face upon a public street, the same may be permitted when the site plan for such development is approved by the Planning and Zoning Commission so as to comply with the State requirements for platting. No parking area, storage area, or required open space for one building shall be computed as being the open space, yard, or area requirements for any other dwelling or other use.