cramer,
Where are you from? There are lots of places to buy one, but it if is very large, shipping can eat you alive. There is one about 2 mi. from me that I was thinking about buying stuff from but instead built a ghetto one (old windows, wood I had laying around, some GH plastic and didn't spend but a couple hundred dollars on it. Wise decision because we plainly do not get enough sunlight from mid-December to early Feb. Trying to heat and light it both would mean toms would cost $5/lb.
But, I am looking to having all the room and then some I need to start a few thousand plants as well as being able to prolong my growing season until early December.
Mike