Make sure u have a proper contract with the owner. U have to convince ure parents that u are serious and committed. In all weathers. Up at all times. The horse come first. It’s not easy. But so worth it .
Show them you are responsible enough, if you have any other pets try to take care of them as much as you possibly can to show you are able to take care of your animals.
Show them that you can show responsibility for the horse by taking care of any other animal and then make a schedule