Home occupation provided that more than one-half of the floor area of one story or the basement of the principal structure shall be devoted to such use. No merchandise or materials, either assembled or unassembled, shall be received into the residence for the purpose of merely storing and/or reselling. No machinery or equipment shall be used except machinery or equipment which is usually found in the home and which will not cause electrical or other interference with radio and/or television reception. 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 said use visible from the exterior of the building so used.