Riding on the back of an untrained horse is like driving a car that does not have any brakes. You can take them out for a test run, but you may come back dead. Even thought the horse’s intentions are good, if he doesn’t have experience, you are riding around with a creature that weighs over a thousand pounds and likes to do whatever he wants. As an investment, horses are more of a liability. The horse has the potential of hurting someone and his resale value is next to nothing.
If you have an untrained horse, he can be dangerous.