When a domain name that was previously registered expires, it goes through a grace period that allows the previous registrant one last chance to reclaim their domain before it becomes available to new buyers. If the previous registrant still has not renewed their domain after the 77 day deletion process, the domain name will officially expire and enter the Aftermarket.
The second option requires a bit more time and effort than a 301 redirect. You could do a mini overhaul of the site and turn it into a microsite for your main domain. This option is good for exact-match domains for your targeted keyword, and there are other reasons for going the microsite route that Rand's highlighted in his post about root domains, subdomains, subfolders and microsites. This strategy also works better if the old domain has decent rankings for the keywords you're targeting.
@ib2 @T-3D I've been a domain investor for over 10 years and have been very successful at it. There's a lot more that goes into it then just registering a domain name and hoping it will sell. You can list your domains on Godaddy auction listings or on premium listings, I've had a lot of success with those. Some good resources are namebio.com, dnjournal.com, namepros.com and others.
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”.