If you’re serious about domain flipping, one of the best strategies is to buy expiring domains that auctioned on the market such as GoDaddy Auctions. Make sure you pick domain names that have good traffic, backlinks and SEO metrics, or domains with the generic niche. Expiring domains with a potential for profit can be found using BuycomDomain.com, this is a free website/tool that helps you sort through the domains by different metrics (age, traffic, backlinks, domain authority etc).

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.

However, I'd argue that most people in the business really struggle as they don't understand what makes a good domain name and what's a bad domain name. While I do not work in this field full-time, I can say that I can make a living of it, but it's probably because I don't ask for absurd prices (e.g. randomword247.com domain name for $8000 is just unrealistic and won't happen) and therefore can sell domains easier. 
Finally, we’ll look at a bit of a different animal in the expired domains world and that’s pending delete. To do that just click on the pending delete button which is right next to the Go Daddy Auction’s button. What this does is it shows you domains that aren’t quite deleted yet. So, they’re right before they get into this deleted category in expired domains. They’re going to be deleted, so they haven’t been renewed by whoever registered them, so they’re going to get dropped.
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.