Our insurance companies (Three actually) have unique programs that will insure 5 doors or more. For you that means 5 single family homes or 3 double rentals or a 3 unit and 4 unit rentals that equal 5 doors.
Many insurance companies will want separate insurance policies for these risks but landlords can now “bundle” them on 1 policy. It does make sense for easier bookkeeping for landlords, who dislike the financials that come along with being a real estate investor.
So successful real estate investors will use this to reduce insurance costs associated with rental property. You do get a preferred rate when using this 5-door or more program, so very useful for landlords.