A fascinating book I read was called Gangleader for a day.
It was the story of a sociology student who spent several years studying a crack gang in Chicago that he had encountered while trying to study low income african american communities.
Sadly, it was bereft on information concerning the illegal gun trade, but it did have some interesting tidbits. First of all was the fact that the leader of the gang never carried weapons, he considered it too risky, he depended on his guards and footsoldiers to protect him. Average gangmembers had to ask permission to carry, and were issued the guns by the security head of the gang. They weren't allowed to buy thier own weapons, and they weren't allowed to carry while making or selling drugs.
There was only one man in the entire story who managed to stand up to the gang in any form, and that man owned a store. The gang wanted "protection money" out of him. He had a rifle on the wall, and paid two homeless men to watch his building for him. They never managed to get the money out of him, and were even forced to reign in their younger members from terrorizing his store.
The real fascinating parts came from the tenets of the projects that the gang operated in. Of course, the gang ran tight relationships with the supervisor, to ensure that the tenets weren't armed. The super was on the take from all the tenets, turning a blind eye to any scams, crimes, or black market businesses. The tenets were lying about their income, because if they made too much money they'd get kicked out of their apartments. The men stayed away from the apartments, for that exact reason. The only men who could stick around were the unemployed, the gangmembers, or the retired. Men with jobs had to hide the money they made, otherwise they could get kicked out or have their rents raised.The women faced the same situation too. The super used the gang for grunt work(Like fixing up the place, repairs, etc). Even the homeless were charged an under the table rent just for the opportunity to sleep in the stairwells.
Basically, everyone was stuck lying about thier income. Otherwise their rents would go up, or they'd be forced out on the street. The only way they could make more money was side jobs. (Everything from selling candy to selling drugs to prostitution) Since they were already doing all this illegal moneymaking and hiding, they couldn't go to the police for anything. So they had to go through the gang or the crooked supervisor (Who would in turn bill them for the service) for any kind of justice or recompense. It was a dirty vicious cycle brought upon by the very socialist welfare system that had been put in place to 'help' them in the first place.