Home occupation or office of professional persons, provided such professional person resides on the premises. Not more than two persons, other than the resident of the premises, may be employed by such professional person and not more than 1/2 of the floor area of one story or the basement of the principal structure shall be devoted to such use or, if conducted in an accessory building, the area of such use shall be limited to not more than 1/2 of the floor area of the principal structure. No use permitted by this section shall result in any use operating in this zone in other than a building strictly residential in appearance. Except for permitted signs, there shall be no physical evidence of such use visible from the exterior of the building so used.