In residential buildings otherwise covered by this chapter, where the owner has publicly established and carried out a legally valid policy of renting exclusively to elderly persons, said owner or any person enumerated in Section 13.24.030 hereinabove shall be exempt from the provisions of this chapter as to families with minor children; provided, however, that deviation from or abandonment of said policy shall automatically subject said owner to all the provisions of this chapter. (Ord. 5655-NS § 1 (part), 1985)