stinky's right about being able to break it down and bud luv is right about framing out. A great compromise is to use galvanized deck screws. Like I mentioned in the most used tool section, I love my drill. I use it all the time. As a grower it can be your best friend. I find my setup is in a constant state of upgrading and I can't imagine doing it without...but I digress...
Build yourself a closet. Having the headroom is great and you can have a shelf above the light for storing water while it dechloronates (dechlorofies?) if using soil.
You can make a fake room in a day and no one would ever know it was there. (As long as it isn't in your living room) People will think it's your water heater or some shit.
I have a spare bedroom that I use the closet in right now but I will be moving out into the main room I think. I will just basically set up a table in the middle and hank my light from where the ceiling fan is now. OK I'm rambling from the sleep meds.
Good luck on the build yiGity