Adding Payment option for Customer's Listing

I am working with a Client who has installed DirectoryTheme and wants to set-up users to have their own account and listings. But each listing has a sale item in which they want the customer to be able to accept payment from the listing item. No, at this point, I can’t recommend a cart, I need to try and work with what they already have in place. I am thinking something as simple as the customer just make and add their own PayNow buttons and add them to the listings. Any less obvious suggestions? If this is the route to take, will there be a way to add this field separately in the listing and will there be code conflicts?

And assistance you can provide would be great!!

Thanks!!!

P.S. Aaaw, I can’t believe I’m a newbie here. New board? I know I’ve posted before…