Amazon Marketplace style website

Our plan is for a website to serve a particular niche and item in the collectables market. There are numerous dealers who sell this particular type of collectable, and we'd like to create one online marketplace where dealers, collectors and those looking to offload theirs can list their items for sale on the website. The seller will not pay to list their item, and the item will remain on the website until it is sold. When a buyer purchases the item, a fee will be deducted and the remainder of the money passed on to the seller who will then ship the item(s) to the buyer. The general structure we're looking for is very similar to Amazon Marketplace, where many people may be selling the same item, and can set the price they're willing to sell it for. The buyer can then choose which seller to buy from based on the price and condition of the item, as well as the seller's feedback score. We don't have a very large amount of cash to spend on an initial outlay, so we are prepared to offer the chosen developer a large stake in the company with a share of all profits. We fully expect this project to be very successful as we are a team of online marketing professionals and I personally have a strong background in the industry for this particular type of collectable. I will be happy to answer any other questions you may have about this project but will not be able to exclusively name the specific nature of collectable until we have chosen a developer, in order to protect our plan.