Head to the marked area at the Northern edge of San Andreas. Once there, head for the marked area. You will find a short tunnel leading into a hobo camp, Dignity Village. Go inside the camp, going over to the right. You will find Curtis Weaver there. He is in a blank tanktop, with red and white suspenders. Curtis will send some of his henchmen after you. Kill them but do not kill him.
Curtis will run off in the fighting so move quickly through his people. Follow the marker to catch up to Curtis as he flees into the hills. Stun him or run him down and point a gun in his face. You do have the option of firing said gun, but there's more money in bringing him in alive.