Horses are not covered property
Standard homeowners forms exclude livestock or limit them to a token figure, and an animal worth five figures is simply not insured under one. Equine mortality and major medical are separate products, and so is the liability that follows a horse.
Anyone who rides creates liability
Boarding, lessons, training or allowing a friend to ride can all be read as an activity your personal liability was not written for, and the commercial-use exclusion is where those claims die. The Arizona equine statute is no substitute: it protects an owner only on specific conditions, a signed release among them. If money changes hands in any form, say so before a loss rather than after.
The Hassayampa runs when it runs
A river that is dry most of the year still floods, and flood is excluded from every homeowners and renters policy sold in Arizona. Barns, tack rooms and equipment sitting on low ground are the expensive part of that exposure.