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.
it can be profitable,i'm selling domains and i can tell you that all providers loose money selling domains,we compesate it with  hosting plans but if you look just domain selling where providers buying domain for 7$-10$ and selling it for 0.99$-5$ ...well like say we compesate this with web hosting plans and other services,also on when some one renew domain but since even renewal is done mostly using cupons...than giving free domain with web hosting is best solutions.Well like i say it can be profitable if you want work with domain,buying domains for 0.99$ and than work with it and you can earn nice money.

In today's SEO (2015) the answer would be a big no! With changes to the google algorithm and the constant updates panda, penguin, what's next...., much of the "keyword url" power is now gone. While there was a day when it made sense to buy a good named .com and expect instant indexing, not so anymore unless the site is very strong coming in ,which in that case you'll drop a minimum $50k. If you are willing to drop that kind of money and the site has a high domain authority, it might make sense as long as it matches whatever product or service that you're trying to sell. Just my opinion...
Referring domains for anchor phrases usually reveals similar information. What you really want to look out for is whether or not the site has been picked up by a spammer in the past. A lot of times these expired domains were dropped, picked up by a website owner who then tried to rank it for keywords like Viagra, Cialis and whatever. You obviously don’t want that kind of domain.
Domain investors build a portfolio of valuable domain names, and attempt to sell them at a profit. Both Sedo and Afternic offer domain marketplaces (also known as Domain Listing Services, or DLS) for investors to advertise their domains to potential buyers. Once the seller and buyer agree, the aftermarket platforms then facilitate the purchase and transfer of the domain(s). As an Enom customer, you’re entitled to list your domains for sale on Sedo, Afternic, or both at the same time. Get started

Quite a lot of the time majestic trust flow will be great but ref domains below 10 but when I check ahrefs its considerably higher for ref domains. Without ahrefs I would of passed over these domains and missed out. Worthwhile addition if your building a lot of pbns. I also use linkultra backlink for my final spam check as it checks language,site type and if backlinks are comment, profile spammed etc enabling me to check if the backlinks of the domain are solid very quick.

The backlink profile of a recently-available domain is a double-edged sword. While some expired domains have been well cared for by their previous owners and have high-quality links from reputable websites, some contain quite questionable backlinks. The worst case scenario is that the domain was merely used as a link farm to strengthen a major project in a satellite domain network and has already been penalized by some search engines.
Hey, the possibilities are endless when it comes to domain flipping so do not think that all profitable domain names are already taken. At this time, almost 90 million .COM domains have been registered, so people tend to think that there are not many good domains left. That is not true since you still have the opportunity to incorporate two or three word target keywords.

For the following TLDs you can now find a expired/deleted domain list. .gi, .gl, .gy, .hn, .ht, .ky, .mu, .om, .pf, .qa, .rw, .sb, .sm, .sn, .st, .sx, .tc, .tl, .ug, .uy They also show up in the Deleted Domains (last 7 days) list and in the Domain Name Search, however they are not in the pending delete list! I do not have a working droplist for them yet, so that is why they are not released in the pending delete list yet.
Another point of concern is that many people feel that squatting or registering domains is unethical. This is because many web developers have a hard time finding relevant domain names for their projects since most of them have already been registered. Many corporate giants also frown upon the domain flipping industry because many domain names relevant to them are already registered.
If you buy a dropped domain from Snap or Namejet, the backlinks seem to be worthless for SEO.  They are valuable for traffic if it's targeted to your site.  Go ahead and 301 redirect into your site because it's the traffic from the back links that is worth something.  I use the Google URL builder to redirect these names so you can see the domain the traffic is coming from.
I did this last month, snagged a great domain that no one else found and got it for $69 because I waited until the last moment to place my pre-bid. Flipped it within a week for a little over $1,000. And probably could have gotten more if I sat back and waited 6-12 months, but a bird in the hand… (plus I like to keep turning over inventory and maintaining cash flow).

There’s an important distinction to make here between domain flipping and website flipping. The latter mainly refers to buying and selling full websites. By full websites, I mean websites that actually have content and more often than not have traffic and revenue. When buying and selling websites, the domain name matters less as the main value there is the content, traffic, revenue, history/reputation, sustainability and growth opportunities. The same can’t be said for domain names where you’re just selling “the name” and hence it’s all that really matters.