Selecting a roommate before committing?

So I recently received a message from a potential roommate from my favorite university, and I am not sure if I should reply or not. While my “dream” school per se, it is a little expensive so I do not know if I will for sure be attending. What should I do? I already submitted my housing application for this school because they have a first come first served policy, but I have not sent in any sort of enrollment deposit due to the money issue already mentioned.

Reply politely, say you haven’t made a commitment to attend the school yet, but that you are pleased to hear from them over email.