Never built one myself, but iIf you search this area of the forum for the phrase “paint booth” for the past year or so you’ll get dozens of posts on the subject.
Try here:http://www.modelpaint.tripod.com/booth2.htm for a good basic rundown on booth construction. Also, do a search here on the forum. You might have to go back a few months, but this topic has been covered extensively.
I just completed my booth and the cost was about $150.00 and change. I used a Dayton motor (4C445) which rates at 495cfm. It’s a large booth, but I’m quite happy with the out come. Everything that I used was purchased at Home Depot (except the motor). The plans that I followed were from a FSM article…I change a few things to suit my needs and now I’m ready to start painting![:D]