There is a garage in Bohan... But can't seem to so something (it's on the map but nothing happens when you go near it)
As neok182 said, that is used for Stevie's car delivery missions (you get them after all 3 islands are open and you've done Brucie's 10 car missions). After you get the 30 cars Stevie asks you for, you can sell any car you steal by parking it in the garage (not that you'll need the money by that point in the game).