Need to be sure you include the "unknown budget" and never take the optimistic approach as it is better to have money left at the end than writing more and more checks that were unplanned for.Again, if you can walk through an actual property and compare notes with someone that does it in your area (key factor), you will be way ahead of what a generic book can give you.

I am currently in Hong Kong, and there is no way I can or will invest here as home prices compared to rent yields just don't make sense according to any of my calculations.

Not as many compared to coastal towns after a Hurricane, but still some.

I've attached the median list price for Detroit here as well to compare to something like Cincinnati. 

Prices are still relatively low compared to many other metros, and rental demand remains strong.I built my portfolio to 12 doors there while living in Detroit (now back in California) and have seen firsthand how the right strategy can still work.

And lastly, I search FunishedFinder listings nearby, find comparable properties, and track the listed rent for a few months (does it increase, decrease?).

You could be in an expensive market, like LA, but you inherited a property or you got a killer wholesale deal or subject to and the numbers could be very attractive compared to buying off the MLS for full market price in the same market.

I would factor in time to travel to any market, but AZ is relatively quick compared to the east coast. 

This plays into the affordability issues for tenants by allowing them to live in nicer neighborhoods for less money, yet I get monthly revenue comparable to short-term rentals.

Risky too compared to just holding stocks or bonds.I'm not even worth that much money so I have to ask the more experienced and successful investors on this forum: what keeps you going?