In my dreams, I'd find a 5-plex, decommission 1 unit, and have a 4-plex at low financing costs, but my confidence in achieving that reality has diminished, given the preponderance of manufactured housing.

In Austin this is unheard of...40+ out of pocket and diminished cash flow.  

The refi will have the previously mentioned costs, and subsequently raise your payments on your current house (diminishing cash flow).

I also had the advantage of coming from a capital markets background so in that sense I was used to (A) working with high achievers, (B) delegating and (C) understanding that talented people need to be paid exorbitantly (the pain of paying doesn’t diminish especially when money is tight).

The bad news in my case is that a year after we replaced the compressor on my 20 year old heat pump unit, it finally started to leak elseware and the heating cooling capacity diminished and we determined it was time to replace. so hopefully your compressor buys you some more time, but know that other issues can still develop.That timeframe is frustrating but relatively reasonable.

All that being said, the Governors do not have the right nor do they possess the authority to diminish our constitutional right to legal recourse, unless they declare MARTIAL LAW.  

I do agree that your cash flow will be tough especially if you add management but for me its a hold because if I consider your selling  of your current property and buying costs of the new one, then the advantage of the new market with less taxes diminishes. 

Also, most investors use dividends as income rather than reinvesting them, diminishing their overall return.Choosing between real estate and the stock market depends on what you’re comfortable with in terms of the level of risk you’re willing to take, but I am a firm believer in real estate over investing in the stock market.

Is diminishing returns a real thing in STRs?

I believe in the Law of Diminishing Returns.