It is more like doing small quests for them. Whenever you get into an alleyway scuffle (bring lots of companions with good civilian gear). You get some loot of whatever workshops the local gang lords own. An example is when I attacked a silver workshop. I ended up with a good amount of Silver. And another asked me to go to Prosos to fence some stolen goods. Simple travel for 800 some coins. Granted this still may risk you getting caught by locals snitching on you to the kingdom.