Re: AR-15 sale
Learn what you can about the "straw man statute". When I worked behind a gun counter (which has been about 8 years ago) the rule basically was : if you sell a gun to anyone that you knew was buying it for someone that was not supposed to HAVE a gun then you were in it up to your neck.
I am not a lawyer so keep asking and CYA.
GRAVITY. It's not just a good idea. It's the LAW!