OP, for a reality check: what level of horse and showing are you doing now, and what do you envision doing as an adult?
If you are a top junior rider now, showing nationally, and want to keep up at that level, it’s very different than if you just want to have a medium nice horse and do the local two foot six.
Honestly I dont think that many working adults play at the highest levels of h/j because either you ride every day, or you pay an extreme amount to a coach to keep your horse tuned up so you can show on weekends. It’s not a game for the 6 figure 50 hour a week young career person. It’s for the independently wealthy.
However, the amount of cash needed to buy a nice enough local horse, get lessons and training as needed, and show locally, is very dependent on region and cost of living. So are important things like how far is your commute to work and to the barn.
Housing costs also figure into it. Because your horse money is what’s left over after you meet all your other necessary expenses. Where I live, the price of a one bedroom city condo will get you ranch acreage 6 hours North but there are few jobs there. If you commute an hour a day, that’s a lot of gas. Etc.
So you can do horses on much less than say $150,000 a year. But you likely can’t live in a big high cost metro area and compete nationally on $150,000 a year either.
The other reality check: what are you good at? Are you good at numbers, finance, math? How do you know? The top people in any field do pretty well. The very lowest tier struggle to make a living. Yes, there are computer programmers, MBAs, accountants, etc., who hadn’t made much of themselves due to whatever. Most people fall into the middle tier. So look at average salaries not top salaries.
If you are a young woman, realize also that most well paying fields remain dominated by men for various reasons, and you may not advance as fast as the equivalent young man.
But you also need to be good at your job, you need to have natural ability and to find the field interesting, and to be in sync with the prevailing corporate culture.
You may also find a niche somewhere surprising. I took a winding path to become a professor in a field I was talented in and loved. Only 50 % of PhD grads in my field get permanent positions. I was lucky along the way. I could afford a fancier horse and more competition than I do, but my riding interests have morphed a different way.
Also finally we dont know where the big money will be in 10 or 20 years. Presumably tech, finance, engineering, but in what sectors? Things change and evolve. Find a direction you have a passion for and stay flexible.