I live in Southern Alberta and have a salary similar to your highest earning potential and I would find it challenging (if not impossible) to own a horse and compete at the upper levels. The cost of living here is really expensive, an acreage suitable for horses is over $1 million and then you would either need to trailer out or bring someone in for lessons which is pricey. Even if you rented an apartment ($1,200+/month) and boarded your horse ($1,000+/month), there wouldn’t be much left over to pay for upper level competitions that likely involve a lot of travel. I half lease (expenses only, no fee) and compete in 6 or 7 national competitions a year (lower level show jumping, little to no travel required) and find this is basically the MAX I can comfortably afford to do. If I owned my own horse I wouldn’t have much, if any, budget left for competitions.
I don’t want to discourage you though, there are a lot of people who are much better at living modestly than I am, and who can make their equestrian dreams work. If I were you and had the opportunity to choose a career path, I would aim for one whose highest earnings potential was greater than 100K, $100k just doesn’t go as far as it used to, and it’s only going to get worse.