Basic Auction Site

I am wanting a basic auction site desgined. What i require within this site 1. Memebership sign-up (e.g Gold Memebership) 2. an internal messaging system for the person who won the auction to be able to message the seller (needs a coutdown timer to cut off after 7 days so they only communcate for that time) (also user unable to delete messages but timer runs out it automatically deletes) 2.1 users have a feedback page of what other users think of them (without sales info just the dates of sales and the users experience) 3. credit card payment options (For memebership) 4. Banner-ad slots for non regestered users (removal on membership) 5. Wanting a backend something easy to modify all parts of the website. 6. Search function to search through site for specific items 7. the budget is 100USD