Fully enclosed structures for the sale of goods at retail or the performance of customary personal services clearly incidental to retail sales. No wholesaling, fabricating, manufacturing, converting, finishing or assembling shall be permitted except as incidental to such retail sales. Not more than five operatives shall be permitted in any personal service shop. No public garage, gasoline filling station or dry-cleaning or rug-cleaning establishment using combustible fluid shall be permitted, except that combustible fluid may be used with the incidental cleaning of spots; no laundry, secondhand clothing or furniture store, pet shop, animal hospital, veterinarian, live-poultry market, billiard parlor and/or pool or storage of motor vehicles outdoors for sale or for rent shall be deemed to be included in the uses permitted herein, except that a receiving and delivery office for laundry and dry-cleaning shall be permitted, provided that no such work is done on the premises, except that there shall be permitted a headquarters and garage for an ambulance service operating not more than two vehicles and serving the general public, whether or not operated for profit.