Only one principal building may be erected in the R-1 through the R-4 Zones. In all other zones, related compatible buildings under one management may be erected, used or occupied, provided that all other open space, setback and coverage requirements of this article are met.

No new building shall be constructed on or any existing building altered or moved onto any lot for use as a dwelling when there exists on said lot a building which is being used for dwelling purposes. No building other than a structure permitted in and by this article shall be constructed in front of or moved to the front of a principal building situated on the same lot.