House hacking is a great strategy. by decreasing your living expenses for your primary residence, you'll be able to save much more money to invest and accelerate your wealth creation.

To decrease this amount and allow me to take out a higher mortgage for a new primary residence I want to refinance to commercial 30 year mortgages for all properties.

While it is the right thing to consider the downside, rent decreases of 20% are highly unlikely.

When one of by duplexes or tri-plexes go vacant my cash flow decreases but the other unit(s) still cover the note.And there are other investment strategies as well. 

Easier to manage and a decreased risk of Tom Foolery. 

You can decrease or completely eliminate your monthly housing expenses, cashflow on top of that, gain appreciation, benefit from the tax advantages etc. 

If you are not raising the rent this is not necessarily a good solution because it may decrease your net cash flow. 

You need to increase your income or decrease your expensesIf you can increase your income this house won't matter.

Does anyone have a story around investing in a “dying city” meaning steady population decrease, steady jobs decrease, and generally not a lot going for it?

At one point they got a whole load of donated NEW dryers; these were gas dryers.The good news is that around here lumber prices have decreased significantly from their crazy high over the past year or so.