It is much harder to sell names no one has heard of. Short names have the highest value — they are rare, easy to sell and bring substantial profit. Basic and common domain names, which can be relatable, or arouse interest in the market are the best. General names sell thick and fast and also bring considerably higher profit.  Names that are easy to spell will attract buyers, and provide good opportunity to make a decent profit. If you know you have a good domain in your hands, then you are likely to make good profit by selling it.
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.