A suspiciously high number of backlinks from some related niche websites that aren’t too great in quality. In my opinion, this could be an indicator that the domain name was using a Private Blog Network (PBN) service or their own PBN to boost their authority…this blackhat tactic can work, but it places your domain name at risk and the PBN owner could pull backlinks at any time.
Listen to expert domainers on domainsherpa.com. Read anything by Michael Berkens, Frank Schilling, Eliot Silver, Morgan Linton, and Ron Jackson. Watch YouTube videos on domain investing. Read blogs like The Industry News Magazine at DNJournal.com. Search #domains on Twitter. Go to industry conferences. Understand the Google Keyword Planner tool inside and out.
There’s an important distinction to make here between domain flipping and website flipping. The latter mainly refers to buying and selling full websites. By full websites, I mean websites that actually have content and more often than not have traffic and revenue. When buying and selling websites, the domain name matters less as the main value there is the content, traffic, revenue, history/reputation, sustainability and growth opportunities. The same can’t be said for domain names where you’re just selling “the name” and hence it’s all that really matters.