Article Selling Script

I require a script similar to the one found on constant-content.com. People should be able to purchase articles from a directory of articles to choose from using paypal. Admin would have the capabilities to setup the directory structure. Please quote a price that would allow an admin to enter articles into the backend system only, and a price that would allow article writers to become a member of the site and enter their own articles and prices into the system to sell as well. Script should allow for a partial view of the first paragraph and half of the article to entice the buyer, and then "hide" the rest of the article. When a buyer is interested, they should then hit a paypal button to go directly to buy it, with instant delivery after purchasing it (Paypals IPN program). Please post completion time and bid.