In P districts, no building, structure or land shall be used, and no building or structure shall be hereafter erected, structurally altered or enlarged, except for the following purposes:
A. Off street parking lots;
B. Parking buildings; incidental commercial uses may be approved by the commission when such uses are entirely within the building and are incidental to the use of the building for parking purposes;
C. Buildings incidental to the operation of a parking lot, not over one hundred (100) square feet in area, to be used only for purposes of maintaining the lot and to contain no provisions for residential or commercial uses. (Ord. 1000 § 30.10, 1955)