@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.
.ac .ae .ag .ar .at .au .be .bg .br .by .bz .ca .cc .ch .ci .cl .cn .co .cr .cx .cz .de .dk .do .ee .es .fi .fm .fr .gd .gg .gi .gl .gs .gy .hk .hn .hr .ht .hu .id .ie .il .im .in .io .ir .is .it .je .jp .ke .kg .kr .ky .kz .la .lc .li .lt .lu .lv .ly .ma .md .me .mn .mu .mx .nl .ng .no .nu .nz .om .pe .pf .pl .pm .pt .pw .qa .re .ro .rs .ru .rw .sb .sc .se .sg .sh .si .sm .sn .so .st .su .sx .tc .tf .th .tl .tn .to .tr .tv .tw .ua .ug .uk .us .uy .uz .vc .wf .yt .za
If you are feeling ambitious, you can link each of your domain names to its matching “buy it now” purchase page at one of the marketplaces. Another more sophisticated option would be to “park” your domain with one of the leading domain parking companies, such as DomainSponsor or SmartName and enable their built-in “for sale” message and contact mechanisms.

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”.