What type of business are you considering of building something on using the domain name?Is it something you believe in and willing to put your all, how much can the monetize with the website, etc..Ask yourself much questions before proceeding to finally selling it.Also, it doesn’t matter if a different company is using a different extension.It means you have upper hand to get their traffic if you build something using the .com.Good luck
2) prerelease auctions.  These are domains where the auction venue has contracted with the registrar, like Fabulous or Moniker, to auction off non-renewed domains.  Just before a domain enters the pending delete process, it goes to a private auction to any person who has backordered the name.  Some people feel that back links on these type of auctions still provide a SEO benifit. My testing indicates that there is zero SEO benifit when these domains are redirected into another site.  So if you get a domain with "pink squirels" in a lot of achor text to a domain and then point it at your domain, you don't rank for "pink squirels"
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?”

I don't necessarily agree with some that dropped domains don't have value for SEO purposes but either way one thing you can do is to check out our tool for finding auction domain names (the tool has a database of domains available buy from GoDaddy and SEDO and also give additional SEO criteria to look up for the domains like backlinks, Compete data, CPC, Google stats, Alexa stats, etc. and there is also an option to schedule auction domain alerts so that you can be notified via email if a domain name meeting criteria you specify gets put up for sale) or you could use our tool fo domains dropping soon that shows all domains dropping in the next 5 days that way you can be ready to snap them up right away.
But in general, the best and easy way to sell a domain is to go with a marketplace. There is many popular marketplace dedicated to selling domains including Flippa and SellDom to sell your domain (full disclosure, I’m working on SellDom). The advantage is to leverage the popularity of that kinds of services in hope that someone will find your domain and buy/make an offer.
By default we show the following metrics - Age, Ahrefs Domain Rating, Moz Domain Authority, Moz Page Authority, Moz Trust, Majestic Seo Trust and Citation Flow, Alexa Rank, Moz Referring Domains, Majestic Seo Referring Domains, Open PageRank, SimilarWeb Rank, SEMrush Monthly Traffic and Domain Price. Apart from these there are around 40+ metrics that you can see by customizing columns
The market-driven principles of the domain trade mean that a domain is only worth as much as the buyer is willing to pay. It is for this reason that criteria such as market potential and usability play such central roles in determining prices. Values can change at the drop of a hat. The price of a domain that was once of little interest to anyone in years past can skyrocket once, for example, a newly founded company takes interest in that same name.
It is mind boggling how local search engine optimization has grown from a tiny market to a mammoth industry within a span of ten years or so. This is also one of the reasons why focusing majorly on local names is profitable. From doctors to pizza parlors to salons, everyone wants to see their business thrive on the first page of Google Search results with the help of target keywords.
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.
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”.