Question:
Are the apartments on campus ONLY for graduate students? Or can undergraduates apply to live there too (ie sophomores)?
Answer(s):
Yes, undergrads can live there. I happened to get an apartment-style dorm my freshman year in Will Vill. I know several undergrads who have apt-style dorms in Reed Hall.
If you're referring to Bear Creek Apartments, yes sophomores and above can live there. If you're referring to family housing, then I believe people who live together must be family members.

