I will be refinancing two off my five properties to get cash out to buy another asset.

However, in this case, heirs can cut me off once they have the property.

Remote control and locable thermostates,  water leak detetors and main cut offs.   

You should not calculate that in your review honestly.Curious if you have the cash for that debt why not just pay it off as the interest is probably burning a big hole in your pocket

On the flip side, I could charge everyone "retail" rents and get retail, one-off clients (tenants) who will cost me a higher % in comparison to the % increase in income, leaving me with a lower net.Businesses are about building and maintaining relationships that are beneficial to both parties.

Run off from neighbors roof is causing wood siding on my townhome to rot.

This could get you 6-8 units if you shop patiently which is a great starting point.Please do not send any money off to companies that advertise real estate "syndications" online.

I'd saying following your experience and scaling off of your flips would make the most sense as you can use skills/knowledge you've already cultivated.

The part I don't yet understand is that if I had a tenant paying my mortgage for me for years, and it ALSO gained equity, how I am so far off any ROI. 

I really think this strategy can work for anyone and can really help launch you off into the direction you want to go with real estate wether that be cash out refinance, HELOC, another FHA, conventional, BRRRR, large multi family , single family, arbitrage , STR, MTR, LTR etc..