User uploaded content help

[f.p.]

Hi guys,
I'm not sure if this is the right place for this post, feel free to redirect me if it isn't.
I'm looking to make a site where users sell items, I want the users to be able to be able to upload their items and then sell them, ideally I'd like to be able to use an auction style script but I could also just have a 'buy it now' button

The help I'm looking for is what is the best language to write this in, or a free cms that has some of the features available, I'd also like to be able to automatically take a small percentage or nominal fee from the seller only if they sell their item

cheers
fp

[asdfghjkl]

Go there http://www.getelastic.com/add-to-cart-buttons/
It may be help you.