<p>Hard to say how much storage you need. The school wants you to buy their hard drive, which is silly. You should be backing your important data up digitally (via Dropbox and a small external) and physical media (DVD/CD/BD) if you’re worried about it.</p>
<p>If you play games, you’ll need more storage. But if you’re considering a mac of any form, it looks like you’re not a gamer so you’re probably good. </p>
<p>Installing the required software could take 10+GB, OSX probably takes a few GB, and if you’re dual booting Windows, there’s 5+GB right there not including the rest of the Windows software.</p>