I did it, and I will never do it again. My horse was extremely well scooled, I did the junior hunters and big eq on him, he was easy to ride, went in straight lines and was an all around good horse. After I leased him out, he stepped down due to his age, and he took care of less experienced riders, he became extremely dead mouthed and heavy on the forehand, would change leads whenever he felt like it, would stop at fences, and grab the bit down the lines. It helped with expenses, but that was it. It took me months to get him back to normal again. This is not to say every horse is not cut out for the lesson horse life, but keep in mind, many different types of riders will be on your horse, this means different flaws and different ways of going. Some horses handle it well, some don't. I personally wont do it again. I would find a lease to one person who gets along with my horse.