On year one it will be similar as CoC but as your tenant pays down your mortgage, your equity increases (which is a good thing) but your Return on Equity will decrease.  

As you move further from the city, costs will decrease.

Just saw this on Trading Economics:"The US unemployment rate decreased to 3.5 percent in September 2019 from 3.7 percent in the previous month and above below market expectations of 3.7 percent.

Just know that it's not requirement nor does it doesn't necessarily increase or decrease your chances of success as an investor.

May not increase your income by much like you said, but could decrease your vacancy % and look nicer in pictures.

While $500/mo is nothing to scoff at, the cost to convert would be $60k+ (or 10 years rent), and I would decrease the resale value by probably 25-30%, which in this neighborhood would mean over $150k in value LOST, by spending $60k.  

I am trying to avoid any unintended consequences . . . for example, may adding an ADU in a fairly upscale gated SFH community decrease the desirability of the house for prospective buyers when I am ready to sell? 

With the growth in equity and decreased principal we are now in the process of refinancing into a lower interest rate and conventional mortgage to remove this added expense.

Not sure if I can put a link in here so google it, Chicago controls.My concern is the heat that I pay for, They can set the ac to whatever they want.When we put these in shortly after acquisition- we significantly decreased our gas bill.

@Mikael WinklerYou can protest, and if you do, you are actually quite likely to get a very small decrease in your taxes.