If I am correct you talking about selling hosting or reselling but you may tell me if I am wrong. The best way I found was to find a seller with cPanel\WHM, then you can get a program called WHM AutoPilot, but some of this is very expensive and tricky. Any way, that program will do almost everything for you plus theirs a company that it works with to let a user buy a domain name during sign up.
Please tell me if this is any thing like you was looking for.
Thanks for all your help but I need one that is all in one.
To clarify you mean you need a billing/helpdesk/live support all in the same php/mysql system correct? The billing/helpdesk is easily found however live support in many cases is normally an independent program, however if you got modernbill you could integrate in kayako esupport which I believe does have live support in it (depending on what version/features you purchase for it).