The most important thing is to try the horse thoroughly before you purchase it. The buyer must be sure its suited to the job you will ask of it. It's never a good idea to buy a horse sight unseen or to buy a horse from someone with whom you are totally unfamiliar. The next step is to conduct a thorough vetting. If the horse will be offered for resale, the vetting must be scrutinized even more closely (there are certain things on a vetting that wont bother you but may bother someone else!). After that, the rest is up to the buyer to provide good management of the horse and to train it responsibly.