My advice, as i was in your position a little more than a year ago, would be to put the AR idea on the backburner until youre 21 and have your class A, then go to The Mill and buy what you wanted. When i was in your position i pondered an m1 garand, then an sks, then i finally bought a pump shotgun and decided to wait and save my money. Although i was pretty bummed having to wait.

I was told by a friend to purchase the SKS, but i didnt feel the need. That being said, it might be your best choice if you want a semi auto bigger than .22. Considering they have an internal magazine, they are still lots of fun to use. But their prices have gotten higher and they are slightly harder to find, although gunbroker and that other NE firearms forum always has good deals. Good luck man