If you have no idea where to start, but you'd like to start a startup based off of the CRM, I'd start with

http://www.paulgraham.com/articles.html

and

http://www.amazon.com/Startup-Owners-Manual-Step--ebook/dp/B...

and see if that knocks out any ideas. There are several possible ways, but with CRMs, it is difficult in my opinion because the ones willing to pay good money for a CRM are the ones already looking at Salesforce CRM, and the other giants.