Here's an old post on search engine roundtable that claims google's policy is to discount previous backlink juice when a domain changes ownership. I'm not convinced whether this is actually true or something Google says to discourage excessive domain buying / 301 redirecting for SEO benefit. The comments above seem to give varying opinions on this matter. Would be great to get to the bottom of that one!
When I first started online, I'd register domains that I thought I could develop and sell at a later time. After learning my way around the cloud, I realized many of the domains I'd registered are pretty much useless, or so I thought, and I let them expire. Come to find out several of these domains have been picked up by parking sites and are being offered for sale for thousands of dollars! Now I'm not saying they're actually selling for the asking price, but I learned my lesson. I never allow a domain name to expire. I add content to it, backlinks, some AdSense and try to sell it for something.
Length: This is pretty self-explanatory. Generally the shorter the domain name, the more valuable it is. This difference in value decreases exponentially as the name gets longer, though. For instance, the difference in price between 3 and 4 letter domains are significant, while the price difference between a 7 and 8 letter domain would usually be much less significant.
There are many different ways to make money in the Domain Name game, but rather than skim over half a dozen of them at no great depth, Buffet takes a detailed look at Domain Flipping, one of the simplist and most effective ways to make money online. He lays out a step by step plan to guide you through the process, as well as a list of free resources that are invaluable.
Buying a trademarked domain name could get you into a lot of hot water. Best case scenario is for the trademark holder to force you into handing the domain over and call it a day. Worst case scenario is you get into a legal battle and end up spending an arm and a leg. This is why it might be a good idea to use the United States Patent and Trademark Office’s (USPTO) website to check for trademarks if you’re unsure about a domain name.
They see a domain’s price tag and they can instantly tell whether it’s under or overvalued. This is probably the most important skill one should have in this industry. Neil Patel has an interesting related quote: “The most important thing to remember when buying sites is that you always make money on the buy, never the sell.” In order to successfully do this, you must be able to spot undervalued domains. This is what will ultimately translate for you into a handsome profit margin when you get the opportunity to resell the domain for its “real value”.