Ok, I understand now.
A post further down suggests that you get a USB network adapter. Good Idea. Make sure it's supported by Windows 98. Install it and update the machine with your cable modem.
All that said, it doesn't get him on the internet. That's another leap. Using the windows built in "get me on the internet" is a sure path to failure ;). The problem is, you can't get a dialup unless you have a connection. You can sign up for a netzero or whatever from your home cable, go to his location and dial up from there.
Your cable provider might have dialup on the same account for free. Many do.
Thanks!