Chris,
James is correct. We've been down this road a couple of times. Just a couple things:
1. Safety should be of paramount concern when planning your booth.
2. The airflow you generate MUST be able to get the vapors from the point of generation to the outside. Fans, filters, baffles, ductwork, and bends all add resistance.
3. Consider getting a prebuilt booth; it may cost more than your home-made job, but will save you in the long run. Artograph and Mircomark offer several good alternatives.
4. I will shut up, now (Thankfully, huh James?). Go do a search for spray booths in this forum, and you should get quite an education. E-mail me if you have other questions.
Gip Winecoff