Lately I've noticed a lot of questions in Q&A centering on purchasing expired domains. A lot of our members have expressed interest in buying old domains for a variety of prices (some are cheap, some are going for upwards of $50k) and want some advice on what to do with the domains once they've been purchased. I'm no domainer, nor am I an expert in such a business tactic, but I generally recommend one of three different options for an expired domain (and would love to hear more if you've got any).
However, I'd argue that most people in the business really struggle as they don't understand what makes a good domain name and what's a bad domain name. While I do not work in this field full-time, I can say that I can make a living of it, but it's probably because I don't ask for absurd prices (e.g. domain name for $8000 is just unrealistic and won't happen) and therefore can sell domains easier. 
The domain name industry is quite similar to the real estate industry in a lot of aspects. There are end users, brokers, consultants and domain flippers or “domainers”. Domain flipping works similarly to buying a house, renovating it (or even sometimes just sitting on it) and then selling it again at a higher price point. The gist of it is: you’re purchasing a domain name and betting it’s worth (or will be worth) more than you paid for it. If you’re right, you get a nice paycheck and move on. Those who make a living out of this just rinse, repeat, and scale.