Bluehost.com offers "unlimited" storage and bandwidth with their standard hosting package. The nice thing about them, is you can host as many domains under the same account as you want, and I think it's like $150 a year now. You couldn't give each of your customers Cpanel access, but that's probably a blessing in disguise anyway. That way, the burden of doing the hosting can be put on their shoulders, and all you have to do is worry about the customer's webpages all for a semi-reasonable fee. I've had an account with them for years now, and it's been my preferred method of including "hosting" for my freelance customers.