REWARDS - Nothing
Head to Avlea Malvada and you'll see the place is crawling with federal agents. If you kill the target, he will drop the dossier, but an agent will pick it up and take off in one of the helicopters. If the target spots you, he will take off in the helicopter, so either way, you will most likely have to pursue the helicopter with the other.
Do not shoot down the helicopter once it is airborne, as this will destroy the dossier and result in a mission failure. As you're pursuing him, you will most likely head over Area 69, which you do not want to do, as this will give you a 5 star wanted level and harrier jets will come after you.
Follow the chopper until it lands and the guy tries to escape. Land your heli and chase him until you kill him. If one of the guards is driving the chopper, then he'll probably shoot at you when you get out of your chopper. Whoever you kill, grab the dossier and the mission will end.