Tell enough guys who actually know what they are doing that they can workout for free if they teach "classes" and pay them like $40 per "class" so they can get paid to train by beating the crap out of other guys.
Yes, it is a liability nightmare but welcome to the gym industry.
have em sign a waiver at the door that they may get hurt and then pinch their ego a little and they'll all act like tough guys ans sign it..when someone gets hurt, no liability he's signed the waiver...trust me