Attorneys are very tight with title insurance companies so you won’t have to look far. 

https://www.qcnews.com/news/investigations/unfinished-business-multiple-homeowners-claim-nc-builder-took-bank-draws-cash-and-left-their-homes-unfinished/?

Insurance is expensive, there is a lot of extra maintenance like painting or electric in common areas that don't apply as much with smaller units. 

I look for cashflow to service the debt, repairs, cap ex, taxes, and insurance while the equity grows, my taxes are decreased, and rents are increased to make more cashflow. 

This is also accounting for my increase in insurance costs due to adding insurance to the ADU. 

. - some strategies I've seen California investors use to lessen negative cash flow: house hacking, mid-term rentals (people temporarily displaced from home renovation or insurance reasons like fire), rent by the room, Short Term Rentals. - The ultimate house hack, live in the small ADU unit and rent out the two levels of the main house on AirBnb in San Francisco (I would have thought STRs are oversaturated in S.F. but it worked for them and they stay fully booked).

How much is insurance of these properties?

You know, like any other INSURANCE PRODUCT.  

Insurance companies are taking a close look at building materials, quality, and updates. 

Your insurer could recommend one or you can check Google (and, of course, the reviews).