Which campus will you be at?
If you will be at north campus you may want to check out the northwood apartments. There is a Kroger easily in walking distance, as well as a handful of other places to eat and random stores. It may be a little difficult to walk to other campuses from these apartments. However, north campus and all other campuses are connected by blue bus (totally free without a bus pass), and these buses come very frequently (every 5 minutes during the semesters I think), even in summer it is still quick, but a little bit slower.
See this google maps link for an approximate area of the store and the apartments in question (south of said kroger).
https://maps.google.com/maps?q=ann+arbor&hl=en&ll=42.303373,-83.705864&spn=0.015045,0.030556&sll=42.748946,-84.47619&sspn=0.239004,0.488892&hnear=Ann+Arbor,+Washtenaw,+Michigan&t=h&z=15
I don't know how much those apartments would cost with a roommate, but I have a friend who had a pretty positive experience living there.