As someone who has gone through nursing school, I agree with some folks that this may not be the best time to purchase a horse. I bought an older (16) Arab gelding when I was 16 and in high school. I went from high school straight through a four year university including nursing school (it actually took five years). It is really hard, and I lived with my parents and had no kids.
I did keep my horse through college, but he was a finished horse, training wise, when I bought him from my friend's aunt for $500 when I was in high school. I got a good deal because it was a friendly, "looking for a good home, sell him back to me whenever" kind of transaction. Not your typical horse purchase.
Due to needing to obtain straight As in my pre reqs to get into my nursing program, and then due to the time required from the program itself, I only worked during the summers. I worked out a way to keep my gelding, feed and board, in exchange for taking care of other horses, learned to do his feet myself, really kept costs down. It still wasn't easy.
While I was in nursing school, I rode maybe once or twice a week on the weekends. I saw my horse every day because I had to feed and clean and all that stuff for him and the other horses, but you don't get much time for riding. Summers I was working. I rode as much as I could, but they were just relaxing trail rides on my been-there-done-that horse. I could never have trained a younger or problem horse during those days, no time. He was my stress reliever during those days for sure.
How you can do it all with a hubby and a little kid would be beyond me. I would personally wait until you are out of school and working. Us nurses get paid well, you should be able to save for a really nice horse pretty quickly once you start working. Just MHO.