Buying an aged domain can make it easier to rank in Google. It’s not necessarily about how old the domain name is, exactly. It’s about the way buying an aged domain lets you assume some of the site’s authority. The trick is acquiring an aged domain that has significant PageRank or an extensive, quality back link profile.
The domain does not have to be relevant to your niche of choice, though it can help. You don’t necessarily want to be 301 redirecting the new domain name to your existing page — though that might give you rapid trust and some link equity, it’s usually better to re-establish old domains. To promote your existing domain, create content on the re-established domains that’s specific to your niche.
GoDaddy Auctions are a good place to pick up aged domains. You can go through the listings there and pick out some that look attractive, then use any number of dozens of free and paid tools for checking them out. ExpiredDomains.net, the SEOMAstering Fake Page Rank Check Tool, MajesticSEO, OpenSiteExplorer, and Ahrefs will give you a through picture of the domain name’s provenance.
It’s important to check out the link history of any domain before you buy. Why? Otherwise, you might end up with something that has a seedy, sordid past. In fact, it’s better to get a domain with an established, diverse, and above all clean backlink profile. PageRank isn’t nearly as important. The free version of MajesticSEO works wonders here — check for over-optimized anchor text as well as suspiciously low trust.
Same goes for checking for fake PageRank. Some people sell domains and use a 301 or 302 redirect to point to other high-PageRank sites… plus a custom script that only does that redirect if the visitor is Google. In other words, you visit the page and Google toolbar or your PR checker displays the PR of the popular site, while your browser sees the page on the “faked PageRank” site.
The other thing to watch out for sits with nasty pasts. This shows up in MajesticSEO as a discrepancy between Citation Flow and Trust Flow. A domain name that has many thousands of backlinks but a very low Trust Flow has probably been used for something shady… which you want to avoid.