If you're serious about going to art school, find out what kind of camera your school of choice recommends. Some schools may require that you use a specific brand so that everyone's working with the same camera. Chances are, you're going to want to go for Nikon or Canon, but I suppose it would depend on the school.

Take a look at Craigslist or Pro Photo's used section. There's a lot of good cameras there for not a lot of coin.