I would recommend waiting to own a horse.
I am going to be a junior in college, and I have owned my pony for about a year. It wasn't my ideal situation. I have trained her ever since she came to my barn [four years now] and a younger girl bought her. It was perfect because her family knew how strong of a bond we had and how well she listened to me so they wanted me to keep training her. The girl outgrew her/they didn't click very well so she was going to sell her. I couldn't let her go, so I convinced my dad to buy her for me. He had to just pay for her and I would take care of monthly expenses.
It's very difficult. I don't regret it, but it's frustrating. I'm so busy and between school work, exams [I am an actuarial major and trying to pass exams. Not sure if you know what that is though. It requires a LOT of studying even in the summer], being the president of my sorority, having a boyfriend ... I feel like I'm not doing enough in almost every aspect of my life.
On top of that, I have an 8-5 Mon-Fri job during the summer where I get paid good money, but by the end of the school year [since I don't work at school] I have no money left. So I have no way of saving money for when I get out of college.
It's stressful. I don't get to ride my pony enough. She is two hours away and I drive home once a week to ride [oh look at that! gas money! Hah], and I feel like she needs me much more so it's upsetting.
I still am SO glad I own her, and I am trying my best to make it work, but I feel like I'm always worrying about something.
Your situation may be different, and it may be easier for you, but I really recommend waiting. Enjoy college. Allow yourself to focus on schoolwork and having fun during the best four years of your life. =]