What about option #4 - Redirect your existing domain to the old domain? I bought an old domain that is 100% relevant to my current domain but currently has with very little content. It did have more content fours years ago. The old domain is 13 years old, pr=3, while my current is 7 months old pr=1 and a decent amount of content. The old domain I purchased was not expired though and I do not know if this makes a difference. What are the pros and cons of option #4? Am I correct to think that option #1 would result in no benefit from the old domain's age value and if so why is it not listed as a con, a MAJOR one. Its hard to believe that a 301 using option 1 would give my existing domain 13 years credit but I'll take it if it does.
We do not only have Expired Domains, but you can also find lists of Deleted Domains for a lot of TLDs. Deleted Domains or Dropped Domains are available for registration and can be picked up for just the normal regfee at your preferred domain registrar! All Domains have the typical SEO relevant data, like Number of Backlinks, Archive.org Birth Date and a lot more.
Domains that are indexed on Google and highly ranked are particularly attractive to traders. Other SEO aspects, such as backlink profiles or the search volume of the keywords in domain names, also play a significant role in appraising value. Design can also positively affect the price of a domain. Short and succinct names that are easy to remember are especially advantageous. Endings are further factors that should be taken into account. Top-level domains (TLDs) such as .com or .org are by far the most sought-after endings.
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.

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...

Check backlink profile: If you’re not familiar with what backlinks are, they’re basically any public website that “links” to the domain in question. Since there are numerous shady tactics in the SEO world, expired domains’ backlink profiles should be examined carefully. Check if too many links are coming from the same domain or if links have weird anchor texts/use foreign languages. You can use a tool such as ahrefs for these purposes.

So how do you develop that instinct? NameBio maintains a database of over 500,000 historical domain sales (as of writing this post). They have interesting filtering features by which you can narrow down domains by price range, date sold, keywords and more. Simply sifting through the listings on NameBio long enough will quickly develop your domain appraisal “instinct”.