In the “B-2,” “C,” “D,” “E,” “F,” “G,” “H,” and “I” districts the minimum area of the lot shall be five thousand (5,000) square feet for a one family dwelling; six thousand (6,000) square feet for a two family dwelling; and for apartment houses or buildings arranged or designed for more than two (2) families the minimum lot area shall be seven thousand (7,000) square feet for each family in excess of two (2).