[Aqualung451]

How about a fight level? pay or earn your way in ,you get to stay there until you loose a fight, fail a crime, etc. The level gives better gym trains (maybe free trainers to a point), higher pay outs in crimes, higher points from fighting, etc. But get attacked and loose, your out. Attack and loose, your out. Fail a crime, and your out. Get kicked out and go right back to Down town.
Earn your way in by winning X number of fights in 24hours, X amount of money from crimes, or X amount of gym training in 24 hours. Maybe the top 25 people from each can get in. all others pay X amount per level to get in.