What are the "first principals" of buy+hold rental markets?

[Travis Fischer]

I'm currently deep into the initial learning phase of real estate investing. Like so many others, I'm interested in building a BRRRR buy and hold business over the next 5 years. For context, I live in Los Angeles, grew up in Southwestern WI and fly through Minneapolis a couple of times a year. Those are the markets I have existing knowledge in. I'm currently trying to learn how to assess markets a few layers deeper than what you can see on the surface.

I'm eager to understand what the underlying "first principles" are that lead to a market becoming good for buy and hold rental investing. I understand there are many factors at play which will vary depending on specific strategy (single vs. multi; A vs. B. vs. C, etc...) . I also understand that at a basic level it's the interaction between the real estate purchase market and rental market supply and demand curves which drive attributes like price to rent ratios in a given area.

My question is, how do those two related supply/demand curves interact at a fundamental level and what are the common characteristics or reasons a market maintains a good price to rent ratio? What are the basic "laws of physics" in rental real estate markets when it comes to optimizing returns?

Would love answers as well as references to any key podcast episodes, forum posts or podcasts that cover this in detail. Thanks in advance!