Like I said though, keep in mind that you should charge something decent to host your clients. Biggest mistakes I made were:
1) signing up for a reseller account and then not charging enough over the cost. It became irritating to deal with problems for the extra $5/mo I was getting by reselling the account.
2) giving a friend some extra web space I had for a small yearly fee. Pretty much the same problem.
Beig a reseller carries rewards as well as problems, and you can't just move multiple sites around as easily as one account. Just try explaining why your customer's control panel changed twice and why they get less space now than before, heh.
Of course if you drive the account (behind the scenes), and your customer never sees these things, or you never discuss space, features, etc., then you don't have a thing to worry about, and reselling is a great way to go. (Or virtual server as MikeA said)