Actually street gangs are pretty varied and complex. Alot of the big ones have structures and ranks and also gang leaders and even members vary in ages from mid twenties to their 40s and they engage in a diverse array of activity from drug dealing, robbery,extortion, fraud, cyber crime,prostitution, contract murder and money laundering.As far as legitimate business goes a number of gang members have been known to open up businesses and in chicago they have been reported to have gotten involved with the construction industry. They also have been known to get involved with music production aswell. Alot of these businesses are used to launder money and also as fronts for other illegal activity such as drug dealing.I think people tend simplify gangs into just kids who hang out on a corner sling bags of dope even though that is part of it.