@Nicholas Gray Nicholas, I can't answer your original question because I'm in the earliest, most raw stages of learning about investing but for the sake of moral support, I completely agree with not staying at a job you hate and enduring 40 years of misery for the sake of your salary.

To effectively exploit market variances over the long term, and hence be a real estate investor that endures, it seems like a firm understanding of the industry's economics is important.  

If I can find a good dog sitter for an extended period, I'm thinking of doing my Easy Rider thing (while I still can or endure it).

Endurance, the ability to continue toward your goal even after failure is also required in life and very much in RE.

Ron Cordes, founder of the Cordes Foundation, has defined success as " . . . fully live your purpose in life, and to leave an enduring legacy of having made a difference in the world."  

However, it appears that at least some of the onerous problems you've had to endure are because you signed a contract not good for your financial health (i.e., you likely didn't negotiate well-enough to protect your interest) and/or because of your acquiescence to their bullying.  

And yes problem area properties can be profitable like your instinct says - just be willing to roll your sleeves up and endure a lot of headaches.

I’m sure we will have to endure all of 2021 of protections for tenants.

I doubt we'll see any enduring case law out of it.  

Do not jump in with a rent credit offer, most tenants are understanding and will endure.