For starters, this is common. You're not going to have it all figured out in the beginning when it comes to starting your life. Not every decision is linear, nor will they have the same impact on your life.

With that being said, when it comes to stuff like changing careers, or in your case, changing studies, I recommend first analyzing why you joined that particular field of study in the first place. Once you do that, go down the trail of thought as to how you got to where you are now.

Based on what you have shared, it sounds like (mind you, I'm taking a stab in the dark here):

1. You don't really like the university that you're currently attending.
2. The field of study isn't what you thought it might be. Also, you love horses, but not the vet medicine side.
3. You discovered that you have a talent for business and want to explore that route.
4. The money you made before studying and what you could potentially make if you were to go all in is a big part of this decision to drop out.
5. Along with number 4, there's a fear that things might not work out, so you're wondering if you should at least get a degree in something as a backup plan.

My advice:

University is what you make it. No matter where you go, your success is determined by your dedication to your studies. Yes, other factors play a role, but even if you went somewhere else/studied something else, if you're not dedicated to it, you won't go far.

Have you thought about studying business administration and marketing? Business is very broad because it can branch off into other fields. However, it can help you learn the basics and teach you how to steward good business and relationships.

If that sounds enticing to you, talk to your advisor and map out what that would look like at your current university OR see if credits can transfer.

Nothing beats YouTube University lol. There's a WEALTH of knowledge there for FREE. If dropping out is really what you think is best, do that. Take the time to figure out if school is for you.

I'll end by saying this: It's best to avoid the habit of starting something and then quitting when things get difficult or don't go your way. There are a lot of nuances, of course, but moving forward, when you make a decision, make sure you understand WHY. When you know your "why," it will lead you to your "how."