Park the domain with a domain parking service. Since you may not have content to put on the site, a parking service puts up a dummy page with ads. When people visit and click on the ads, that's money for you. This method works best with popular keyword domains that get lots of traffic. In most cases, you will not have control over what ads appear on your domains.
Buying and selling domain names is an exciting adventure that for some seems to conjure up images of finding hidden pirate treasure or guessing the winning combination on the next Powerball. Stories abound of domains that were purchased for $8 dollars 15 years ago being sold today for millions. Of course, that leads the more adventurous of us to wonder, “How can I do that?”
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”.