I do not send my sale horses out on trial very often, and if I do - they go ONLY to trainers that we have a strong and trusting relationship with.
The trials are structured much like a short term lease. The price is agreed to and paid in full ahead of time. There is no way I will ever let a horse leave my care that is not paid for - too much risk.
The vetting is also done before the horse leaves so that we document the condition and soundness of the horse at the start, and don't have to deal with a situation where the buyer breaks him during the trial, and then wants to return the (now broken) horse "because he's not sound like you said he was." The buyer purchases insurance that names ME as the beneficiary. I don't allow long trials - a week is usually plenty of time to see if the horse will work out in the buyer's program - and they have to use my vet, farrier etc. (I do not do trials out of state or anywhere too far away for me to keep tabs on the horse personally.)
The contract is structured to allow the buyer to return the horse as long as IN MY VET'S OPINION, the horse is returned in the same condition it was in when it left my farm. (This has the benefit of discouraging buyers from over-working the horse during the trial period, as any soreness at all means they do not get their refund.) If the horse is OK and I agree to take it back, I refund their payment LESS the lease cost for the time they had him.
You should be aware that it doesn't take long for bad training and riding to create problems in a horse - even a nice, easygoing sort. There is a huge risk to the seller in offering a trial, which is why most sellers just won't allow it anymore. Too many horror stories.
********** We move pretty fast for some rabid garden snails.
Admittedly I am a "back yard" horse owner (except that my horse is at a boarding barn) and what I mean is that I only own one horse, don't have a big name trainer, the barn we board at is simple but suits our needs just fine, we only do the local show circuit and my horse isn't even a double digit horse if I were to sell. But....having said all of that....there was a time when we did send our horse out on trial and it was a disaster. While the trial person came off as wonderful before she took the horse, she turned out to be nothing but a liar. We had a written agreement and she was all about agreeing to it, until she took my horse. She didn't honor any of the agreement. Needless to say, we went and got the horse and it has taken almost two months to get the horse back to where she was before we let her go. It was a horrible experience and I feel so guilty about giving our horse to someone who I THOUGHT I could trust. I would advise, if you are a horse owner like me (described above) I wouldn't ever, ever, EVER consider doing that again.
No, no and no. We sent a fancy WB mare on a 10 day trial and she was dropped off by a shipper basically crippled with a massive stifle injury (20k mare). We just gave her away as a broodmare.
We are similar to Lucassb. If you do decide to do it, the only thng we have found that works is the person BUYS the horse before it leaves. Paid in full, with cash or wire. Write into the contract that if the horse doesn't work out, doesn't vet, etc, you'll take it back IF it's in THE SAME condition, in YOUR opinion, as when it left. We don't even leave it up to the vet, it's our decision. We can refuse it if there is one hair missing. Risky to the buyer? Maybe. But otherwise it's not worth it to us. We ride the horse, look it over, etc, and ensure it has suffered no ill effects, accidental or otherwise. Since the horse is truly sold, this makes the person act responsibly about the horse, they can't dump it and run like happened to us, and if they break it they own it, so no problem there. There is no insurance required because they own the horse, we already have been paid, so it's their responsibility to get insurance if they would like. We have done this 2 times and it worked well both times.
Otherwise there is no way for you to be compensated for loss of value if the horse suddenly develops a bad habit, gets bad training, loses condition (weight or coat damage), gets injured, etc. It is just entirely too risky!!
If we had had a vet fully examine and do a report on our mare before she left, we could have proved that the injury was caused by the person with whom she was on trial, but since we didn't have a statement of her condition before, it was near impossible to "prove", other than by witnesses, for a lawsuit. I am sure the injury was an accident but that doesn't help us at all...