Online payments for a middleman

I'm new to online payments and would like some opinions on my task. Here is the scenario:

I have a website where people buy and sell digital photos. A seller has a photo and wants to sell it. They create an ad on the site and upload the photo into the website database. Buyers looking for phot开发者_运维技巧os come to the site and buy them. The buyer pays the asking amount and then can download the photo. As the middleman, I'd like to charge the seller a fee or percentage of the selling price. The buyer shouldn't pay any website fees, just the selling price.

My question is - what is the best way to do this? I dont mean programmatically, but what service should I be looking at? As far as I know PayPal wont work because of their fee structure. Im told Amazon payments would work but its sort of a hack. The seller has to set up a business account and then tie their item to my website as a third party sales venue. Is there an easire way to accomplish what Im trying to do? Of course keeping fees as low was possible.

This will work perfectly fine with PayPal.
PayPal offers Adaptive Payments as of a while ago, which allows you to specify 'primary' and 'secondary' receivers (up to 10 recievers per 1 transaction I believe, from the top of my head).

You could thus use Adaptive Payments to set the photographer as the primary receiver, set yourself as the secondary receiver and optionally move the transaction fees onto the photographer as well.

Have a look at this page for more information.