In Ridley Township v. Pronesti, 431 Pa. 34, 244 A.2d 719 (1968), our Supreme Court held that a licensed real estate broker was not permitted to operate an office as an accessory use in a single-family dwelling. The applicable ordinance allowed accessory uses that were "customarily incidental" to a permitted use and defined the "customarily incidental" to include the professional office or studio of a doctor, dentist, masseur, teacher, artist, architect, musician, lawyer, magistrate or practitioner of a similar character.