Unless of course his DSL MODEM IS already a router. Then you have to consider ............
Oh, never mind. Just do like Peter says and buy a Wireless Router and give some teen a beer i-tunes gift card to configure your PCs/laptops up.
And Yes, I did recommend Wireless as the most simple solution but I was afraid to emphasize it to much because Tom was against it and I was afraid beer would stop shipping to PEI entirely due to insulting the Beer God.