Rental Insurance (Umbrella Policies)

I am finishing up my first Brrrr home and in the process of refinancing. My question is about insurance for this and going forward. I will obviously have the "normal" insurances such as property/flood and I want to get umbrella. Is there a typical limit that one company will allow for number of properties under one umbrella? Are there any other insurances that are must gets for the properties? Thanks.