I've got a Linksys cable modem router that does the firewall. I have the [link|http://www.linksys.com/Products/product.asp?grid=23&prid=173|4 port w/wireless] version which ran me $300 last year. It's down to $150 now.
If he's not interested in wireless he could use the [link|http://www.linksys.com/Products/product.asp?prid=142&grid=23|1 port] version by plugging it into his existing hub/switch. It can be found for $60.
My house is fully wired but I picked up the wireless version because of friends who bring their laptops on visits. I replaced my laptop's NIC with a wireless one and would never go back.