Hi guys. Looks like you are really new.
The 2 features that I think are needed for this software to rock will be:
1) Payment Gateway. I would like to see the system to have the ability to accept a current merchant processing account, meaning they already accept credit cards, and the ability to use a system delivered by you. PayPal of course as you will be asked for it. If you need assistance with that part of the system send me an e-mail and I can walk you through all the stuff you will need to know.
2) The ability to capture Credit Card information for offline processing. Yes, it will need an SSL cert and the ability to hold information encrypted.
Those are my initial suggestions.
Cheers!
UberGeek.
UberGeek