It doesn't really matter which platform you choose. I bought a Mac Air prior to starting school and it's been a great purchase thus far. You'll take all of your exams on your own computer via a special browser that's available for either platform. If you choose a Mac I would suggest you buy the Microsoft Office suite just for guaranteed compatibility with the instructors' notes. (You can purchase it from the campus library for a discount once you're a student.) As far as needing a CD/DVD drive for school, it hasn't been an issue yet; thumb drives and Dropbox work just fine.
Their cost of attendance is low, i think.at least compared to one other school i know. So if you don't have any other financial support, you'll be on a very tight budget. Although on the bright side, you wont end up with a huge debt.