Be aware though that there are many modular companies and some are more expensive than design/build custom ADUs.I would also agree with with Andrew, a conversion of an existing space (like a garage) might be the cheapest.Also, check with your city laws on what's an allowable ADU to construct based on your current home and rental regulations for them.Collin

How do you handle the design aspect; do you hire a designer or do this yourself? 

I aint going into it - it requires a much longer novel to explain the diabolical environment that has been designed and implemented and all the people who are complicit without their own knowledge.

Check with your lender and CPA to confirm this will work in your particular situation.

I had a friend drive by the house and confirmed that someone is in fact living in the home and took pics of the exterior for me.

In the meantime, I'm an experienced registered Interior Designer who is willing to help with completing on trend "investment conscious" flips.

With a business that is so heavily dependent on reviews, I can imagine (and my friend has confirmed) how hard it would be to manage other people's properties.  

Zillow, Redfin, and public records all confirm that.

I feel like I am reading that you really need an additional policy that is designed for short term rentals (I know that my homeowners policy will not cover any STR related claims), but why is that the case if I have the AirBnB insurance at my disposal?

Speak with your attorney on this and confirm you are even able to do it and enforce it.