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.
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. 
What is a domain? Despite this word being mentioned so frequently, it’s often unclear what the functions and structures of domains are. Knowing the hierarchical structure of the Domain Name System (DNS) is fundamental for anyone working in IT or in any online industry. We explain the difference between top-level, second-level, and third-level domains, and how you can benefit from subdomains that...

Great post! I tried to repurpose an expired domain to build an authority site (your method 1) – but it doesn’t rank as it should. i checked the backlink profile via majestic and archive.org and it’s clean. also checked the metrics of the competition. with the amount of trust and link juice my expired domain has vs. the competition, it should be on page 1 for those keywords. is there something i’m missing here?
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”.