I need a release form for training/riding a horse?

I am 14 years old, will be boarding the horse with my own colt at a facility nearby. The owner will be paying $200 a month and supplying grain. I am supposed to train him for two months starting in January (so I guess something about Winter should be in there,ice and all). I am supplying the training for free. The horse is named The Imperial Maximus and he is from the Minstril Arabian line. He is 6 years old and is just now being broke in. I want something in to say that she cannot not leave him with me for more than 3 weeks without contact or he can be forfeited or sold. That I am not responsible for farrier work,deworming,grain or injuries sustained without my doing or knowledge. I want it to say after 2 months of training more money maybe requested to cover extra cost and that I also agree that injury to myself will not be held against the horse or its owner.