Site cash system question

[PlymWS]

I'm looking at setting a site up where users will be able to sell stuff to others. I have a few questions about this before I get a license.

Would the following be possible with any of the available mods or would I have to write one / get one written:

1. I would want my members to attach the files they want to sell to the first post in a new thread. There would be another text box on the new post page for the "Price".

2. Then the uploaded photos would produce a thumbnail preview (jpgs producing a non-clickable, resized & watermarked image, movie & text files using a simple icon)

3. The attached files would then be zipped into a zip file.

4. To download the zip file another member would have to pay the price set by the poster.

The funds could be in the form of points which users could buy through an integrated Paypal mod. Users would need to be able to buy points, spend them buying other members' thread contents and cash them in to form a payment to their registered Paypal address.

How much of this can already be done with currents mods ?