There are many risks that would-be domain investors should carefully consider before buying and selling. The three largest risks are liquidity, subjectivity and legality, but there are also many other ranging from misleading appraisals to faulty escrow payments. Would-be buyers should carefully consider these risks before investing in domain names.
There's a lot of guesswork that goes into domain name investing. It's not enough to purchase domain names that are currently popular. Just like a stock, coming too late to the game won't be profitable. You have to think of the future, instead. What domain names might be profitable in the future? Is there a new product or service that may become a huge hit? Where is the future headed?
I OWNED DOMPERIGNON.ORG, incredible, but true.  Lost it, back in the days when internet in India was not a readily accessible utility. And I was a casual domainer.  You had to go to a cybercafe. Did that late in the day, towards the expiry of the domain. No chance of renewal. The domain is now with the owners of Dom Perignon and is redirected to! 
Prospective buyers can contact domain holders directly in cases where the desired domain is no longer available. Most registries openly publish the names and contact data of domain holders. Once this information is gained, buyers can get in touch with domain holders and make them an offer for the name. Sales are also known to occur even when the original domain owner may necessarily have never had any prior commercial ambitions
The less tech-savvy population on the internet is not fully aware of what the term ‘domain flipping’ means. If you are one of them, then this article is definitely a must-read for you. In this article, we will delve into the details of what ‘domain flipping’ refers to, how it is done, and whether it is a profitable part-time business opportunity or not.
If you buy a domain from a 3rd party, the backlinks are valuable.  I always wait a few months before redirecting, so just set up a quick minisite until two page rank updates have passed and then go ahead and 301 redirect.  However, it seems that you'll get the link juice from the back links, the anchor text is ignored by Google.   Buying a domain at Godaddy TDName expired auctions, seem to not count as a dropped domain if you immediately set up a mini-site.

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”.