My brother had a horse which he had to pay over a thousand pounds a month to keep because it devrloped a foot condition! Think about wat can go wrong whil you are still young, is your mum horsey? If she isnt you have no chance
It seems that you really do love horses and are passionate about riding and taking care of horses! I do not know your mother's reasons for not allowing you to have a horse at this time, but perhaps you can talk to her and understand her point of view? having your own horse can be VERY expensive. Not only the price of the horse, but the board, the farrier, the Veterinarian,. any medical expenses, your riding lessons, your tack, riding gear, etc. Maybe this is the reason? Also, about time...as you know, horses take a lot of time, even if you are boarding them. Do you really have time? What about school? I am sure that takes a lot of your time,and all your other school activities, going out with friends, etc? Maybe your mother thinks you won't have enough time? You seem very responsible, and work at the barn, but owning your own horse takes more responsibility than working one day at the barn. I think that a good talk with your mother to listen to her concerns would be a good idea. In the meantime, and since you have a few years until you are 16 (oh! would there be an added expense of a car???), I think leasing a horse is an excellent idea. I know you did it once, but to do it again would give you a taste of ownership without actually owning and you can see how that progressses and if you really do have time/money for it. Any experience you can get including as much work at the barn as possible would be very beneficial to getting experience around horses, and could help you determine if horse ownership would be the right thing for you or not. I leased a horse for a very long time before I got my own horse and I am glad I did. I was very busy with school, friends,, etc, and even went away to college. All that would not have been fair to a horse that I had purchased. Maybe in a few years when you turn 16, you will know better if ownership would be right for you or not.