As a safety measure before you can move those machines out of the unit (likely after your tenants leave) would be for an auto shut off valve - some of them are digital and will do it when they sense any sort of leaks. 

A more accurate measure of joblessness (“C-6”) is still at 12%, while the number of Americans outside the labor force remains just above 100 million.Retail Rental Market Shows Life.

These may not be on the shelf at HD, Lowe's, etc but they can order one.Even if you're replacing with one the same gallon size, measure the closet with your tape measure, and compare that to the dimensions in the new heater's manual, before you buy - they aren't all exactly the same. 

Maybe an oversimplification of what they're saying in the podcast, but if you could refi your house at 3%, and then throw that money right into a general stock market ETF aiming for 8%, then you can conceivably consider debt the asset yielding you a 5% return. 

I'm primarily aiming at cashflow at this stage. 

That's not an argument in favor of investing here, rather just an observation that this should not be the thing that changes your mind because lots of other states are doing the same and we're likely to see similar measures at the federal level as well.

I subtract our the condo fee from rent, and then measure against my buy criteria. 

try and measure it with other professional companies?

We aim for it, even modest cash flow, in everything we buy and that our clients buy. 

I didn't know there was a statistic that measured "peace of mind".