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.

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.. 

Maybe one day I'll be glad I did but that would mean something really bad happened so hopefully ill be pissed off forever haha

So let’s say you invest $50,000 when you are 20, with an investment kicking off 8% interest, at 38 your investment will grow to $200,000, at 47 $400,000, at 56 $800,000, and 65 $1,600,000 (as long as you reinvest your initial investment’s returns).

How much do you have to live off?

The electric has been off so the sump pump would not be functioning.