No development permit for a residential use in the R-7 District shall be issued until the Administrator has made a determination that:
(A) A plan for the future expansion of a principal structure exists and is on file with the Administrator, and
(B) That the ultimate development of the site can be made to include three bedrooms, a car garage and a screened porch, all in desirable locations and without violation of the provisions of this title. ('69 Code, § 7-16.01, Subd. 5)