i'm currently an undergrad at umich and will be starting umich dental in the fall. Here is my housing advice:
most "good housing" (close to the dental school) will be taken by undergrads (the dental school is across the street from the undergrad campus). So then your options are living walking distance from the school or bus/driving distance. I would recommend walking distance, it's nice to walk to school and walk to the library without having to worry about driving and parking (driving in ann arbor sucks, not only is there no parking but students walk across the street without looking and are constantly a hazard to avoid). But if you decide to live driving distance the busses run all the time and housing is cheaper.
Living walking distance is a little pricier, there is tower plaza (nice but more pricey), unversity towers (cheaper, still ok), lots of appartments and houses. I would find another incoming dental student and get a two-bedroom appartment or find a house (either of those options will run you aprox $600 /month plus utilities, tv, internet etc), living on your own (1 bedroom appartment) will run you around 1000/month.
Either way i would get move on housing asap.
Let me know if you guys have any other questions