I want to share my experience with Jenny Yi, an STR designer in case others have had similar issues.

Issues 1) even garage conversion ADUs in single family zoned areas typically cost more to build than the value that they add.  

My 46 years in the real property investment field has taught me that almost all wealth in real estate is accumulated through price appreciation of the subject property owned and amortization of the associated mortgage note(s).  

Can anyone recommend good companies to root cause  and implement solution to fix this issue?

I'm looking to make this part of the retirement stream of income rather than an effort to accumulate multiple properties.

In general it is not worth building a single ADU for a variety of issues but the largest is the cost to add the ADU is typically far greater than the value added by the ADU.  

The vast majority of wealth accumulation is through appreciation, cash flow after rents increase, and amortization. 

They may also be able to temporarily relocate your tenant to avoid any other issues.

A smaller paid off portfolio seemed a lot easier to manage so that is the path I was on.. but I've come to the realization if I ever want to accumulate serious wealth I will have to use leverage and scale big. 

This is a very common issue in parts of Milwaukee and I have done lots of basement reinforcing on our rentals.