there are always at least two, these are the funnest missions I have played, since they nerfed mission payouts I generally run around and do these. I happens alot where the crates disappear after the mission or if they are shot during the fight, look for all the white flashing cash on the ground. All crates do have $500 as mentioned above, plus up to $35 per kill, up to 20 kills that I have seen. You can make some pretty good cash quickly, more that a store robbery and not have to deal with the cops. I have noticied recently, that players will ofter come to either assist or get the crates post fight, free guns, cash, recently I have had to fight other players rights after the fight is over, which can be problematic as after you win the gang fight the game pauses for you while everyone else can still cap you. Just and FYI, if not playing solo, grab the cash quick and be ready for a fight when its over.