Rental Insurance questions

[Peter A Bratt]

My wife inherited four rental structures (two fourplex units, one threplex, and one single family home) from her mother. Her mother was a shrewd investor, but really did not spend a lot of funds on capital maintenance, which my wife have spent a lot of 2019 paying for (installing new roofs, new water heaters, etc) stuff that was original for the units (that were largely purchased or built in the late 1980s). 

I am taking over some of the property management of these units, and one issue I need help on is insurance policies for these buildings. My mother-in-law had three separate policies on these various units; one on the threeplex, one covering the fourplexes, and one for the single family home. My gut tells me that there could be some cost savings on having all the buildings insured under the same policy, but I'm unsure what I would need a policy to cover? The three existing policies cover different levels of coverage and have different deductibles. Can folks advise me on 1) what needs to be covered, and 2) what sort of deductible level we should go with? None of the properties have mortgages and are all rented fully. 

Thank you all! Peter