This is similar to house flipping, where a home is purchased and fixed up in order to sell for a quick profit. Unlike house flipping, however, there is essentially nothing to be done with the domain name in order to increase its value. Therefore, the key to a successful domain flip is being in the right place at the right time in order to acquire a valuable domain name before it is given a premium price.
HIM: "Mainly small-medium sized local businesses looking for a way to increase their ranking. Most already have a branded domain in place, and have heard that using a keyword domain can help. Or they have seen a competitor ranking using that method. The problem I face is that they don't have a lot of money to spend, so I get lowballed on the asking price. There have been a few that make a ton of profit vs what I purchased it for, but that boils down to luck: what is for sale, when I find it, things like that."
The most popular place by far is ExpiredDomains.net. The main advantage of ExpiredDomains.net is that it aggregates data from a lot of different auctions and websites around the web. There are also paid services like DomCop. DomCom helps you identify worthy domains faster by displaying some additional data points that allow you to vet domains easily and in a unified interface. And finally, there are services that curate domains they believe are worthy such as JustDropped.com’s newsletter.
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.