I'm completely new to the world of e-commerce and online transactions and, frankly, I'd rather not be responsible for storing credit card information. I am considering using Authorize.net or PayPal.com to make transactions, although if anybody has a tutorial about how to integrate this so that as soon as a transaction is made, my website can receive confirmation and update the database accordingly, please provide a link. I don't know how any of this works; I develop PHP/MySQL websites, but I have no experience with this third-party transaction stuff.
My customers will be billed yearly probably through one of the services mentioned above, which I think I'll be able to figure out. Here's my real challenge: I also need my users to be able to pay each other. Basically, the site will host virtual documents and a user can purchase a document uploaded by another user; once the transaction is completed, the buyer will be able to download the document and the seller will be credited the money.
Any suggestions? I can't seem to find a service for this kind of interface.