Families will be able to buy/setup illegal business of different categories and the more they control, the more will be the market share of that particular illegal business. More market share means more profit income!
Categories can contain:- Bootlegging, gambling etc
The concept can be implemented in different cities, with each cities having mafia groups with their % of market share in different businesses.
For eg:- Hells Kitchen:- X family controls % of bootlegging operations etc..
Maybe importing exporting narcotics that would be sick addition