@Valerie S. as all the posts above reflect, this is normal. 

And I'm not talking anything even remotely resembling a "war zone".I plan to stick with middle income areas where the underlying demographics and culture pretty much reflect the national average.

No, wisdom comes from self-reflection plus solitude.

Virtually every COC calculation I have seen for ADU additions do not reflect the negative initial position and therefore are not accurate (or at least not an apples to apples comparison with COC calculations on most other investments).

Reflecting on this 5 unit project that started in 2008 and ended in 2011 I can say we made the following mistakes:1.

It is 32 units and severely under market rent with a low purchase price reflecting that.

It has an NOI that reflects that concern though.What I’m most concerned about is demand for rentals and it being a “war zone”.

Lower returns reflect lower risk.Outside of return, don't really know how to quantify risk besides gut feel.

Reflect up front about what is most valuable to you - cash flow, appreciation, ability to scale, and let that drive your search. 

They work, but their service isn't as good all the time, and you may see that reflected in your ratings.