Trading Protocol

This is a project to request your bid to develop a TRADING PROTOCOL between Buyer/Seller in a Web Listing Community, like Craigslist. I am opening up a similar listing community where buyer / seller can buy and sell. There will be a TRUST CERTIFICATE that will be created for each user. This Ceritificate will be used during trading until a sale is consumed using payment processors; PayPal, Google Checkout. You will add PayPal and Google Checkout functionality as a processor to complete a sale. You will create a Page - User Request for a Trading Certificate (Personal Information Data validation) and create a Certificate Logo result (Valid, Invalid, voided, expired, cancelled) You will create a User Listing and Orders Page You will create Trading Protocol that will be available in user Listing and Orders Page Make Offer, Accept, Decline, Counter, No Trust Cert. Etc. The Community Listing application is not decided (maybe AJ Square) This will be written IN PHP/mySQL for MAC OSX 10.4 / 10.5 and >.