Best thing is to search your city code for "home-based business". When I called my planning department the clerk said "It's not allowed" but wouldn't cite reasons. When pressed, her reply was "It's just not allowed" which is really frustrating. So I took it upon myself to search the city code which was quite clear that it wasn't restricted, and we know that anything not explicitly restricted is allowed. I know for a fact that cities like San Jose definitely don't allow home-based firearms dealers or even gunsmithing, as written in city code.
Mountain View, CA