HP-Kaumil, yes ModernBill is good but like I stated, instead of going out and purchasing a such system, I would rather give it a god my own self.
OldHomie, if you weren't disabled I may see more responses from you but, lol. The live chat part is still up in the air. As for the Authorize.net/2CO/PayPal/etc. Yes, I would have to make payment modules for things such as to pay invoices, etc.
I am not having a system where you the system is like automatic/instant. I want the owner or whomever to have to add the usernames in themselves and have things go from there. Nothing like PerlDesk, etc. where you are auto-signed up when you purchase something. Maybe have something more if you're an existing client, you can purchase other services through the system, otherwise you need to use the main website for a such task.