If he can't find a complete gun, have him search for a stripped receiver. Most can be had for around $100 or less. NOTE: Do NOT buy one that is marked "PISTOL". He cannot build a rifle out of it!!!
www.rguns.net is a good source. Only $99 for a receiver that has some nice pictograms on the selector. The receiver is a serial numbered item so it will need to be shipped to an FFL dealer for transfer to him.
Once a receiver has been obtained, a AR kit can be purchased from www.model1sales.com Kits run around $550 for a traditional M4 rifle. The kit can be shipped directly to his house.
Done!
If he's into customizing his AR, he can buy a partially assembled lower, then buy a custom upper (like the Adams Arms piston upper).
Rguns has this for $160.00. A very good deal. Looks like you can choose between Black, Olive Drab, or Matte Sand color. Also, stainless trigger group or parkerized carbon steel. It's good to have options!
I think this is the best deal of them all. Buy a fully assembled lower for $205 or one that is dressed out with Magpul MOE grip and stock for $245.
They let you place the order online, and that gets you on their build list. They are backlogged, due to high interest. Still, better to be on the "paid" list than be left holding nothing. The rest of the AR can wait for a bit... those price should NOT be going up within the next 6 months. Oh, BUY MAGAZINES! Hi cap, the better. THOSE will be like GOLD in a year or two! Mags run $10-15 each. They will hit $50.00 when the ban kicks in. That's a $1000 profit!
MARK MY WORDS!