Assignment Trading Website

Assignment Trading/Buying Freelancer Website I am looking for the backend coding and database for a freelance website; much like RentACoder but not nearly as advanced. I want users (Students)? of my website to be able to post homework assignments and bidders (Tutors) to be able to bid on these assignments and in the end the students will choose a tutor to do their homework. I already have a design template ready to use and have some coding done already (you are welcome to continue upon my php scripts or re-write your own from scratch). Features of the website will include: -User registration and security system (2 types of users - Students and Tutors)- -Assignment posting system (Including file uploading and time calculations -Due dates, end of bidding time, etc...)- -Assignment bidding system- -Tutor rating/grading module- -Payment and escrow? system - through paypal- -Dispute system for administrators to settle disputes between posters and bidders- -Tight security framework where all users stay anonymous and no unregistered members can view anything- As you can see; there is not much complicated features; and I am not looking for anything fancy. You do not have to do any layout design; but the requirement is that you must use as much web 2.0 as possible. Such as form checking and AJAX througout the website. As dynamic as possible. As little page reloads as possible. AJAX and Javascripts are a must.