A good rule of thumb for compressors is to buy what you can't afford x2 . I finally got ahold of a good used old Speed Aire, it's rated at 28cfm @ 175psi . The old girl weighs in at 700lbs with the motor on it , took 6 men to get it in the basement . But, I can run my 3/16" nozzle sand blaster all day, and never even get it hot . Go big as possible , regret it a lot less later .....
Sarge