Until it's not.
When that horse you are training bucks off its owner and puts them in a wheelchair.
That horse you are riding for a friend happens to trip and end up out of commission for the rest of it's days.
That kid you are teaching falls off and gets dragged down the driveway, causing hundreds of thousands of dollars in medical and dental care.
I know it sounds extreme. You think, "that would NEVER happen to me". But let me tell you, it DOES happen. It happens every day, all over the equine world.
Here are a few cases for example, although not all professional;
Hilz vs Riedel - A young girl is severly injured from a fall at a friends house.
Young vs McKim - A worker responsible for caring for a horse was kicked in the head while working.
Back Injury After Fall from Horse - A woman is injured during a riding lesson
If you are a member of an organization like the OEF (Ontario Equestrian Federation) here in Ontario, you have automatic coverage for liability involving your horse, so long as it is not a commercial entity. If you are not a member of an organization, your homeowners policy may extend to cover a horse in the event of a non commercial claim. The moment you accept payment for a service you are considered a commercial entity and need a Professional Equine Liability policy to cover you.
A Professional Equine Liability policy will protect you when you are working with horses, for others. It is imperative you carry this type of policy if you are training; teaching lessons, catch riding, boarding, and even grooming. The upfront cost outweighs the potential long term devastating life crippling costs you may incur, should you be found negligent in the event of a claim. If you are living in the USA, you better be sure to have coverage. The most lawsuits are recorded in America.
If you are practicing any of these activities on your own property - you better be sure your farm or home policy covers you for that also. Most property Insurance Companies need to know if there are commercial activities happening on the property they insure - including training horses, teaching lessons, etc. If they are not aware of this and you have an unrelated claim, your claim could still be denied.
The same thing applies to auto insurance. Do not ever take money for trailering (unless it's gas splitting), without a commercial auto policy.
In Ontario - the average Professional Equine Liability policy costs about $800.
But don't take my word for it. Do the research. Get educated. Call a broker, get a quote. Get covered.
Insurance is something no one wants to think about or pay for, but I can not emphasize enough how important it is to cover your ass(ets), whether your home, your horse, your future.
A few links to some good Equine Law Blogs which cover equine liability, not just professional: