While buying up a ton of domains seems like a great way to make some extra money, the real world results show that it is very hard to make that process profitable. As with any industry, you will have those "golden moments" when someone you read about made it into a million dollar a year business, all while sitting in the comfort of his own home. That could be true, but he probably consumed a lot of alcohol and lost a lot of hair doing it.
ExpiredDomains.net gathers all the information you need to find good Expired Domains that are Pending Delete and you can Backorder. Depending on the domain extension you can search through thousands of domains every day before they get released to the public and pick what you like. ExpiredDomains.net currently supports 449 TLDs. From the classic gTLDs like .com, .net, .org to Droplists for ccTLDs you can only find here and now we even support some of the best new gTLDs like .xyz and .club.

The first is the link profile I and actually took this example carbondsystems.com because it looked like a pretty good choice. It’s from 2003. It has some links, some age and it’s in DMAS and looked at the link profile in DMAS. So, you just copy and paste the domain,  the home page it to here, click on the search links button and this will show you all the links to that site.
Your domain name registrar may provide you with a free one-page Website tool, which you can use to create a “this domain is for sale” landing page. Alternatively, you can create a single page (perhaps a hidden page hanging off one of your existing websites) that indicates that your domain names are for sale. You can then forward all of your domain names that are for sale to that one page.

Once you have a name in mind, how do you know if the price is fair? I like to use namebio.com to compare the domain I’m thinking about buying with similar domains that have sold. You can enter the keyword and also use some advanced search features to see a list of names similar to yours, what they actually sold for, and when they sold. You can also research current domain sales on venues like GoDaddy Auctions and Afternic. Finally, Ron Jackson issues a weekly report on DN Journal that covers the top public sales of the week. You can use all these resources to help you price your domains correctly.

Yes! Selling domain is an emerging trade and no wonder if it can develop into an exchange. www.DomainX.org has been initiated with this view. There are some good ideas in the comments regarding which names to buy and how to grow their value. However one must not forget that it also involves a recurring cost (annual renewal) and keeping many of them might become difficult if you are not really selling at least a few to cover it. Enjoy free listing at DomainX.org.
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 have one domain name which I never used it and it has .com and I later discovered there is another company with similar name but with .net and they are doing good as once they approached me to sell them my .com which I never did as I had plan to start something which didn’t materialize . its been 11 years now I have maintained the name now I have two options.
You can find the new fields in the Column Manager and the Majestic Filter Tab. Majestic Crawled URLs, Information about the Outbound Links of the Domain and Information about the types of Incoming Links (follow, homepage, ...). Also you can now see the detected language for the website (or previous website) on the domain and the language of the anchor text links referring to the domain. The filter for the website language only includes values with at least 20% and the filter for anchor texts only with at least 10%. When you hover over the column, you still see all values (even lower percentages), but lower values are not used for the filter. If you only want to see domains matching the majority language, use the "majority language" filter. Unfortunately that filter doesn't work in the domain name search

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”.