cpanel isn't needed, have them install webmin, it's free; granted it's a little more advanced, but if you have webmin/usermin/virtualmin installed you can do just about everything that cpanel can do.
And larger sites need more resources, it's a given, and theres not much to get around that; you should think of doing some advertising to help subsidize costs.
I'd be willing to help you with setup/consulting for a fee; it'd be well cheaper than paying for cpanel indefinately lol, i run a VPS with CentOS for my site, all of the current software (PHP/MySQL) and webmin, no need for any fancy overpriced control panel, webmin lets me add domains, add emails, edit users, etc etc etc; it just takes some getting used to...
