Down draft would be expensive. I bought a std booth for for our shop a few years back (I no longer work there). I think Binks was one of the big suppliers of free standing units. It had fluorescent light installed horizontally at a few feet off of the floor, filters in the doors as this was the air intake, filters and fans in the corners toexhaust the fumes, explosion-proof electrics I believe, lockouts on the lights (the lights were tied into the fan so you can't paint without having the fans on), etc. I think it was $30K w/installation.