I am currently looking to buy a horse (my first horse in many years) and am very interested in getting a short trial period to evaluate the horse off-site and have a veterinary pre-purchase exam performed. I know not all sellers will agree to this and I understand why, but in my experience it is very difficult to really know whether a horse is a good match after just a couple short rides.
My question is: Do you negotiate the selling price before taking the horse on a trial or at the end of the trial? What if the trial period or PPE reveals something that decreases the horse's value, but you would still be interested in buying it for less? (for example, the horse is sound but has early signs of navicular disease radiographically, or that the horse cribs in a stall and you didn't know this before because it was kept in a pasture at the seller's place).
So, if you had signed a trial agreement for a purchase price of $5000, but decide that the horse is only worth $3500, is it completely out of line to then ask the seller to reduce the price (of course they could always say no and you would have to return the horse).