I have a similar arrangement with my trainer. She happens to love my horse, so occasionally enjoys joking about making me disappear so she can just have him
I have a an “emergency fund” for the horse, which would support ~6 months of his current lifestyle (boarding, training, vet, farrier, etc). It’s outlined in my will that this fund would also transfer to the trainer in the event of my death. Maybe this is a bit of a “luxury” but I think it’s an important consideration when leaving a horse to someone. Willing a horse to a friend seems neat at the surface, but may also create an unexpected financial burden that some are not able to bear.