Build a Website

Hello, I am searching for a web developer that can develop a website with a native iphone / android app in the near future. For now however, we are focusing on the website only – PLEASE BE CLEAR THAT AT THIS POINT, SEEKING QUOTES FOR WEBSITE, WITH THE ABILITY TO EASILY CONVERT TO AN APP LATER ON. The website that I need is essentially a marketplace that can be traded on. I need users to be able to sign up to the website, have an account, have inventory and then trade inventory with other users. The website is for trading fruit and vegetables, so I need the site to be able to calculate the average cost of lets say… a strawberry, and the average cost of a lettuce and determine a recommended trade price. So if someone wants to trade two lettuces, the site will calculate how many strawberries they will receive in return – based on the value of the items. Users should also be able to sell their goods for a monetary value – and therefore have payment systems such as paypal integrated. **IMPORTANT users must be able to search for items that are currently listed in their area via a map which would pinpoint the location based on the user profile. Users also need to be able to advertise their goods, where advertising revenue will return to the site owner. Advertising would put their items on top of a list, in a 50km radius. There also needs to be a traditional ‘shop’ page where I can list items for sale. I would like a quote for the build, and for ongoing updates and maintenance. Preferably on a system that is not too complicated for me to log in to and update basic sections as I have some experience with CMS systems and little HTML knowledge. So if it were done on a platform such as wordpress or similar to save time, cost and ease of use that would be great. Happy to provide further specifications on request.