If you are going to buy an old domain, beware of risk to fall prey to a PageRank fraud. There is a whole industry of domain selling tricksters who sell old domains with fraudulent or hijacked PageRank.
Without going into details of how they do it (not to let bottom-feeders to replicate this), I’ll just summarise a list of points to check PR validity before you decide to purchase an existing domain:
1.Check PR manually. Don’t trust to what you are said. Go and check PR using Google Toolbar for Firefox or an SEO plugin (such as SeoQuake for Firefox). Make sure it’s the same value as the buyer says it is.
2. Check backlinks. Type in Google link:www.site.com, where www.site.com is the domain you want to buy. A more convenient way to check backlinks would be to use the SeoQuake plugin. If the site has PR=4, then it should have at least 3 backlinks with PR5, or 18 backlinks with PR4, or 101 links with PR3, or 505 links with PR2 or or 3055 links with PR1. If it has a mixture of various PR links, you can use this table for PR calculation to estimate what PR the site should have according to the number of links found.
3. Check Google cache. It turns out that if you redirect a domain to a high PR site, then the redirecting domain displays PageRank of the destination site even for some time after the redirect is removed. This is the trick that domain selling fraudsters use to sell low-PR domains at a high price, and newbies, who don’t know about the trick, readily buy into this. To avoid becoming a victim of such a fraud, check cache by typing in Google search "call recorder app for your iphone". Make sure that a copy of the site saved in Google cache looks exactly the same as what you are buying.
4. Use PR predictor. Bear in mind, the Google Toolbar update PR only every 3 months or so, therefore even though the displayed PR maybe 5, the actual PR maybe zero. Why? Because domain selling tricksters might have bought a few high PR links just before the latest PR update and then took them off. So in reality, the actual domain PR might have dropped to 0. To verify that, use a PageRank predictor either at pagerankprediction.com or link.ezer.com, which should tell you an approximate current value of the site PageRank.
5. Check WhoIS records. Using SeoQuake or SeoToolbar plugins for FireFox, or going directly to Whois-domain-tools check the WHOIS records of the domain. Explore them and see if there are any other domains on the same IP address, or if the same owner has lots of other domains in general. If you see the owner has hundreds of different domains, especially if many of them are on the same IP, I wouldn’t be very reluctant to buy the domain in question.
6. Check web archive. Finally, If all the previous checks were clear, go to archive.org and trace the history of that domain. If you see that the domain used to have a drug smuggler or kinky porn site on it, this may reduce the chances you still want to buy it to absolute zero.