A friend of mine's site was busted down to pr0 for selling links just wondering how long mr g might keep him there ?
Your friend should remove the paid links and submit a request for reinclusion in google webmaster tools but there is no guarantee that the pr will return.
Can't answer the question directly, but I would take kingofsanda's advice to start. However, before I requested a reinclusion, I would develop some really great content, and then try to get some completely whitehat inbound links to it. Show Google that you now want to play by their rules, add value to the web and that independent editorially driven websites believe that your site has value. Best of luck to your friend! -Chris