Scholarships and pell grants will only cover so much though. If you plan to go to one of the bigger universities, then you are looking at astronomical tuition that will only be taken care of in part by financial aid. If you are hoping to get a full ride to a big university, then you will have to be superb at either a sport or be nearly a prodigy in a given field and you would spend all your time practicing or studying and would have no time for a horse anyway. I am not trying to shoot down your dreams at all, I think it's great that you are willing to work hard for what you want, but I have been in the situation where I was going to college, having to work full time, just scrimping by eating Ramen noodles that I could buy for 14 cents a package and sneaking food at the restaurant where I worked. Between school and work, I was lucky to have time to see my horses once a month. And this was just going to a junior college where every bit of my tuition and book purchases were covered by the scholarships that I was lucky enough to get. I still had car payment, phone, rent, gas, electric, internet, etc. It was incredibly hard and I actually had a breakdown one night at work just from being exhausted and burned out. I don't regret it now but I honestly have no idea how I survived it, school from 8 to 2:30, work from 3 to 11, homework from 11:30 to 3, working doubles on weekends from 9am to midnight.
Once again, I am not trying to plant doubts in your mind, just kinda giving you an idea of what can happen so that you can prepare.