I agree, it's cutting it too close.
Other things to consider -- would you be able to continue working the hours you're working now, once your classes start?
College takes up a lot of your time, you won't have much time to enjoy the horse you'd be working so hard to be able to afford.
Feed might be included in board, but you may find that the feed/hay the barn is feeding isn't adequate for your horse and then you'd be paying additional to get your own feed.
My advice would be to look for a situation where you could half-lease. If that goes well your first year in school and you're doing fine with managing your time and keeping up with costs, then look into a full lease. I think you likely won't even have enough time for a full lease, if you're in school full time and working 5 days a week.
Even better, if you have some patience, hold off on getting a horse for a few years (perhaps as a graduation gift to yourself, after you graduate college?) and save up. With a horse, you should probably have $5,000, at minimum, set aside for emergencies, at all times.
Keep in mind, when you graduate school, unless you're going into a field like nursing, where you can find a job almost anywhere, you're going to have to be ready and willing to up and move, if you get a job offer elsewhere. In this economy, college graduates can't usually afford to be picky about where they take a job. Any time you own an animal, it complicates the moving process. Especially a horse. So it would likely be wiser to wait until you're settled somewhere, before you take a horse on.
If you set aside, say $250 a month, as 'pony funds', you'd save $3,000 a year. If you're in school for 4 years, you could have $12k, saved up, specifically to be put towards a horse and its expenses. That, in addition to your current savings would put you in a much more comfortable place :)
Good for you, for taking the time to consider all of this before just jumping into horse ownership. Many people aren't nearly as smart as you :)