If your leasing application process is thorough and well thought out, and if your lease agreement has been well drafted by your local attorney and if it includes clauses that permit you/your property manager enough latitude to maneuver and anticipate undesirable tenant behaviors, both actions and inactions, and you have operational processes which align with enforcement of your lease, then you've done all you can do to reduce this inherent risk of an undesirable tenant.  

I think you have a good start and sometimes you learn more from mistakes than if all goes well.  

My original plan was to buy 15-20 properties with REI if things went well. 

Well that is unfortunate.

Determine the cost of construction (hiring a contractor in the GNO area is going to start around $165-175/sqft to build) and be sure to include all holding costs, as well as interest in the loan.

But I do have lenders that can offer these in entities as well.

there you go. the problem is appraisal. comparable sales, and your approach to building an ADU against the recommendation of your market. super beginner strategy it's popular in ohio as well but just not worth the investment. 

@Jeff G. some well intended and mostly true assistance posted so far.Let's look at "logical" answers:We're going to assume only 4 Classes - A, B, C & D.- Some people go to F, but what's the point?

That's only if everything goes well.  

@Marc Shin Well now you're getting brave....asking us BPers for design advice.... :-)