I am 18 and out of school but brought my baby a few months before graduation. I absolutely love owning my own horse but it is very very expensive and alot of responsibilty. I am lucky now I just moved with my parents to a house where we can keep our horses in a 5/6 acre pasture but I was boarding him before. I brought him for $1000, paid $450 right after to get his shots and teeth floated, $25 every 5 weeks (he is barefoot), $100 board a month (but I had to go out every morning and night before school and after work to muck and feed), $10 for a 50lb bag of feed (which is very cheap!), $7 per bale of hay, then you add in the cost of tack (I already had tack too- and guess what! It didnt fit him so I had to pay $600 for a saddle that did), grooming supplies (i spend $75 on a gallon of flyspray), if you have to buy barn supplies (buckets, etc), and the list goes on and on!
I am fortunate that my parents would help me if an emergency happened that I could not afford. And if I ever couldn't support him they would keep him as their own with their two horses, but honestly I would starve myself before Andy (or any of my other 7 pets) went without lol.
I work full time making $8.50 (about $600 every two weeks) and I can barely afford him. And you can defiantly forget about fitting in with your friends at school (having new clothes, getting expensive highlights for your hair, cell phones, things for you car, etc). And like I am sure everyone realizes - it is ALOT of responsibilty and work. Sometimes I wish I could just come home after a hard day of work and go to bed - but I can't because I am 100% responsible for my boy and I have to take care of him to my best ability.
And it would not be easy to just sell your horse if you got into a sticky situation, think of how attached you would be!
I am not trying to discourage you but maybe you should wait until you have a solid job that you can depend on a monthly income.
And sorry this was so long