I don't know if you know this, but you can buy a pistol, just you are more limited on what you can do with it. Im 20 and I bought a used H&K USP, 9mm from a private party. One problem is buying ammunition, you cannot buy it from a FFL. But there are ways around this. :P
Sure, you may not be able to carry it anywhere but your house. However it also gives you time to get good with it.