Then he's going to need to pay more than 500$. You can get a powerful tower for 500 bux, but you build it yourself. Tell him to get his mom to build it or something. You won't get nearly as much power buying a shitty pre-built 500$ tower than you would building one.
However if he wants a facebook/college computer, just go to walmart and buy a dell. Maybe having them yank him back and forth when the shit breaks and the warranty has holes in it might make him want to learn how to make his own PC.]
Also, in reply to your above post:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814130580
That card will run any game on the market currently, and it's cheap. Seeing as he is not a gamer, that means he wont need to upgrade his video card for years to come if he buys that one.
You identify a good video card by the reviews and specs:
1GB DDR3 Video Memory = Will run anything today (It's not the most powerful card out there but it will)
PCI-E 2.0 (Pci Express) = That's the slot on the mobo it fits into, every up to date mobo these days will be able to fit it.
And then look at reviews. Some cards are good but burn out fast, waste of money even with a warranty.