Located in East Oldtown, Eddie is your main contact in the cartel, he'll be the one you contact to order more drugs, make sure to pay him back though as owing him money means owing money to the cartel.
He'll also let you know whenever anything interesting happens. EG: Unlocking the ability to buy hideouts from Mike Byers, unlocking the furniture store, unlocking Jamie's Drug Store etc.
Eddie is presumed to be a nickname with his last name being "Edwin". First name is unknown.