it doesn't work quite like that. he's going to need to find a company to host his domain for him. hosts run anywhere from about 10-25 bucks a month for basic domain hosting service. they will provide him with a set amount of web space, personal email accounts for his domain (ie.
[email protected]) and some other stuff.
what his domain host does for him is to assign a numeric IP address specifically for his actual domain name so the two are linked and his website comes up when someone types either the IP address or domain name. the monthly hosting fee thereafter is for the host to keep the IP and domain name linked and for the webspace and traffic.
i can't think of any free hosting companies off the top of my head, but domain hosting companies and places that give out free web space are two totally different things.
hope that helps some.