How about those cheap carports make out of conduit and blue tarp? you could close in the sides with 3ml plastic from the hardware store.
Pakrat, I'm sorry but I disagree about the fan blowing in. When the fan is blowing out, it tends to suck air in through all kinds of cracks and crevices - loaded with dirt. If you have a fan blowing in with several filters on it, the dirt from those cracks will be flowing towards the outside, away from the paint - because you are literally pressurizing the paint booth. You have to be sure that the fan that is blowing in is pointed away from whatever you have to paint, so that it won't tend to stir up dust. The filters also need to be wetted down to trap the incoming dust. Professional paint booths are set up this way, to keep airborn dust to a minimum.
