Many colleges offer piano classes, even for nonmajors. (My university does, for example). These can be an excellent introduction to the instrument, and you can even earn credit for taking them! So check your college catalog. And if your parents are paying tuition, you don't even have to foot the bill.
Self-teaching can be very difficult, especially if you have no experience at all with reading music. My advice, if you can't afford regular lessons, is to find somebody willing to teach you on an intermittent basis, e.g., once a month or so. This is crucial because only an experienced pianist can tell if you are using proper hand positions etc. Many people have warned here that bad habits, once formed, can be extremely difficult to break. Some things are also just plain hard to pick up on from reading, e.g., pedalling.
So if the college classes don't work out, shell out for a few private lessons at first just to make sure your posture etc. is okay before going the self-teaching route. Any local piano dealer will probably have referrals for teachers. Alternatively, you could try to find a music major in your college who may not be a professional teacher but willing to help you learn for a much lower price. Ask some of the music faculty if they have a student they can recommend.