Asked my recommendation about implementing a payments processing backend within their Web Presence my response is look at this first.
http://quickbooks.intuit.com/payments/
This tool accepts payments / invites credit cards … and they have a device you can attach to your iphone or ipad to scan cards.
What I like — is that the few extra pennies it costs, it integrates to Quickbooks online and they own the security backend.
If / when you have time — I’d like to hear more about how you’d like payments to work.
As a rule of thumb — at our scale, especially — I do not recommend attempting to incorporate payments online within your Web Presence. Too many security issues, too many risks.
Let’s find a better way — sending a payment request via PayPal or from QuickBooks Online.