He could make the best of an open warehouse by growing the plants larger. A bathroom is going to be too small. Since phoenix already mentioned something about building a frame, I took it that phoenix is not looking to stay in a bathroom. Might as well grow 5 plants as big a possible to take advantage of the fact that no one can see in, there is plenty of space and probably plenty of power. I guess what you're thinking of is something like a three stall bathroom but I still think that is small. But since I haven't seen it, kind of hard to say. It's an opportunity to grow indoor trees. That's how I see it. BTW, I didn't say "set up without walls," but just to avoid spending money on panda plastic if it isn't going to be an advantage in reflecting light. At least one frame still needs to be built in order to support the sodiums or MH, even if the grow takes place in a bathroom because you can't screw HPS or MH bulbs into a conventional socket (if there are any), and most commercial bathrooms use flouro anyway, which means there won't be any incandescent style light sockets. So in my opinion, take advantage of the open space and secrecy by using the open area, build at least one frame to support the lights, and the rest as noted above.