If you want to make a living with horses, a horse *breeding* course is not the route I would choose. Very, very few people actual make a living breeding horses, for most it's a hobby or a side job. For a young person, with no capital, I don't think it's a viable career route.
Good instructors, especially those that have a knack with children, can always make decent money, but it's best if you have some credentials. Instead of the horse breeding course, I would look at an instructor's course, then after that, be an apprentice or assistant instructor to someone with an established business.
Speed Racer made an excellent point though. Riding instructors are on their feet all day, work in all sorts of weather, and do a *lot* of lifting, carrying and pulling. And it's still the least physically demanding horse career I can think of. Do make sure you're up to the demands of the job.
The other good news is that instructing is something you can do part time or in addition to another job. There's even an argument that it's better to do it part time, so you have another source of income that isn't seasonal or weather dependent.
The bad news is that 1.) you'll be self employed 2.) no insurance, income protection or other benefits. It's a gratifying but hard way to make a living.
So, in short, I'm not telling you you have to give up your dream, but you are going to have to modify that dream to fit your real circumstances. I wish you all the best and hope you find a way to make it work for you.