I agree with the other poster about your life stage and going through tremendous changes - like going off to college, roommates, finding a rental that takes pets, etc. Plus, once you have the amazing freedom of young adult life, you will always have to come home after school/work to a dog that has been cooped up all day, and a small little play session before you head out with your friends will not be enough.
I think that it's awesome that you want a GSD - or any dog, for that matter.
Another thing to think about for the next two years, is who will be home with the dog during the day? By that, I mean, you may have all the greatest breeder selection, training plans, etc --- only for the dog to spend most of its waking hours with a parent/sibling who basically un-does your training. If they are fearful of the dog, then the dog will not grow up to be what you want him/her to be. I know this, because I'm CONSTANTLY training my family to train the dog properly. They all mean well and LOVE dogs, but they unwittingly can encourage unwanted behaviors.
All in all, it's your decision (with your family). Whatever you decide, do NOT buy a $250-500 puppy from a back yard breeder! Do your breeder research and get a healthy, mentally sound pup.
Or, for your situation, perhaps a rescue dog would be an excellent choice. That way, you know what they look and act like as adults, and you know what you are getting, in those respects.