Ian is a character who appears in the data files, but not the actual game. He can be added to free-roam through hex editing, and he will appear in the New Coventry area.
He is white, with facial stubble, a plaid shirt, and a blue headband. Nearly all of his dialogue includes the words "yo" and "gangsta." Like Nate, he may have managed a shop that was cut from the final game, perhaps a fireworks shop, as he mentions them when saying goodbye to Jimmy. His dialogue is mostly unfinished.
He could have worked at Rocket in My Pocket.
His voice actor is unknown, as he wasn't listed in the game's credits. The data files list his position as "Associate," and give his name as Ian.