yea, they are super cheap...i think i saw a network card for $10 new the other day in a magizine and your son needs cat5e cable which you can buy at Manards (i just heard that from a friend tonight, he said that it's on the second floor if your manard has a second floor) for cheaper than like bestbuy. The cable is the cable that you install walls, but it's most definally cheaper! but here is a link to a 14Ft cable:
http://www.bestbuy.com/site/olspage.jsp?id=1051384717238&skuId=5364241&type=product from bestbuy.
If your son has a laptop, he would probably much enjoy if he had a wireless network, but those are pricey. If he has one of those, he can do homework on his bed, out in the lounge, in the cafiteira (probably not, but possible),