The only guns you ever need to worry about selling are ones that are rare, unique, or have had special work done to them, especially if you are buying to fund another gun. For those who can't afford to have large gun collections (like me), the only way to have a wide variety of guns is to buy and sell. If you get lucky and pick up something special, don't sell it. But a glock 19 isn't in that category. If you get a serious case of buyers remorse or want to pick another one up down the road, you can stop in to any gunstore on the planet and pick one up.