"Buying or Selling the links" with other websites are not good for Google prospective...You can go through the link exchange columns of DP forums and interact with a lot of webmaster for link exchange....
I am really curious why do you want such keywords! Sometimes, just getting HIGH PR backlinks won't be enough to get a good ranking. Example: you get a backlink from a PR7 website with 1,000 other OBL's. Your backlink is totally USELESS! Especially if the blog/website is NOT in the same or at least related niche! I would pay more attention to more natural ways to get good backlinks!