What complications can arise from a courthouse marriage for the sole purpose of having marital status?

A friend of mine was telling me that if she were married, she would qualify for the tuition reduction she would need to go to college. I said I wouldn't be bothered by just getting a legal courthouse marriage for a few years, as long as she agreed to end it when she didn't need it. Other than the fact I can't marry anyone else (not a big deal right now, I'm 20), what problems could arise from this?