Classifieds type of Website System

We have a client whom needs a classifieds type of website to allow people to post advertisements and pay etc. I can't give too much detail here but this is what we are looking for..... Site Design - We will supply you with an idea on what we want the site to look like, and you will need to come up with design concepts and design the front end. Functionality - The site will basically work like a classifieds. It will allow people to create adds for their products, upload pictures, set the prices, add descriptions etc, and then pay for their advertisements using credit cards or Paypal etc. There will be multiple categories for the advertisements etc, but think of it like an eBay site, but without the auctions. We need the ability for them to come back and edit their advertisement if they want to. Full functionality specs will be provided, but that's it in a nutshell. This client is very important to us, so we need professionals who can do this job, and do it well. We don't care if you use Joomla, Magento, or some other off the shelf product. As long as it's good, looks good, and works well. We have the hosting facilities, so we don't need the site hosted - it just needs to be able to run on Apache and MySQL. Pleas let me know if you have any questions at all, as we are happy to answer them. Please don't bid for this if you are not sure you can do it. We need this done well.