Most colleges and universities allow one aquarium around 5-10 gallons, which is more than enough space for a single betta. Your school's housing website should have pet guidelines and tank size regulations.
As others have said, it's really not much work at all and the initial investment, even if it seems a bit pricy at first for everything, will go a long way.
The betta care sticky (http://www.bettafish.com/showthread.php?t=49160
) is a great resource, as are the people here.
Also, remember to shop smart....those tiny eyedropper "betta conditioners" that cost 2-3 bucks? You're better off buying a bottle of PRIME for a few bucks more that will not only last the entire academic year (probably longer), but is very good in quality.
One final word of advice.....I would recommend taking a few weeks to get settled in before buying a betta. The first few weeks of school are often the most hectic, and your focus should be on making sure you have your schedule set, books, knowing your way around town and campus, meeting new people, etc. before having to worry about taking care of a pet.