If you can find a good way to manage 25,000 website without cPanel I'd be happy to try it. I agree it's unwieldy and completely takes over your server in terms of how you have to work around it but in the web hosting industry the automation and integration it provides, not to mention the almost idiot proofing for customers, it's hard to beat it.

Regarding the original question in this post. I agree with most others: Don't do it. Sign up for an affiliate program, make some side cash and let the hosting company deal with the tech issues that will keep you up 24/7 otherwise.