I am looking to purchase an AR15 here shortly, but am unsure on what the requirements are?

I was in a little trouble when I was 18 but have been fine since (no felonies, no violent crimes.) I don't want to go somewhere and try to buy one only to be declined and look like an idiot. I was young and dumb, looking to hopefully get my old lady into shooting so we can both go to the range!

Thanks!