Here’s what you DON’T want to do: Target prospective buyers based on their perceived economic status, without any insight into the industry you’re targeting. “Lawyers seem to do well,” you think, “maybe I should start selling names to them.” So you rush out and buy a bunch of domain names you think would appeal to the law firms you’ve identified as potential buyers. Without knowledge of the space, you may not know that the American Bar Association and other industry-specific organizations set rules that govern some aspects of legal advertising. You’re not going to strike gold selling names your target buyers can’t use.
I've seen some people comment about losing the link value of domains that have expired and picked up, but what about non-expired domains? Let's say a competitor is going out of business and they still have a year or two left, and we buy their domain and site. Is there a risk changing registrant info and registrars, even if I keep their site up and mostly the same as before? I was under the impression that I'd want to keep it under their name so as not to hit the uber-reset button on the domain's inbound link value.
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.