35mm SLR versus Digital SLR?

[biguniverse]

I've been using point-and-shoot digital cameras for the past 4+ years now. However, I'm getting ready to take a Basic Photography course and they require a 35mm camera.

My question is, should I borrow a 35mm from someone for this course instead of investing in a new 35mm camera (e.g. Canon Rebel)? Or, will I need the 35mm for anything else in the future that I cannot use a D-SLR for (e.g. Canon 10D)?

My interest is in nature photography and possibly selling large pictures (e.g. 20" x 24"). My fear is that I won't be using a 35mm beyond this course because I'm really interested in digital much more.