Not surprisingly, subsidized student accommodation is normally a lot cheaper than market rentals. Quality varies widely, depending on the year the facilities were built. Old residency halls can be dull and depressing, while new or renovated facilities sometimes offer very high living standards.
Unfortunately, there are only a limited number of available subsidized student rentals. You apply for them through the local student services organization (Studentenwerk).
Make sure to apply as early as possible (if possible, before your arrival), since many student service organizations have waiting lists. There can be waiting periods of up to one year, depending on the region and your requirements. For further information visit www.studentenwerke.de
Private student halls of residence also rent out rooms at favourable rates. Local student services organization will be able to provide addresses.
Shared apartments: For those who are coming to Germany alone, WG's or Wohngemeinschaften (shared living arrangements) are often a good option as you can live cheaply and meet new people. WG's are most common among students and young professionals, but you can also find shared apartments among 50-60 year olds. Living in a WG obviously means sharing a kitchen and a bathroom. Be aware that WG-Zimmer are often not furnished.
University guest houses: If your host institution has a university guesthouse, you can also have your name put on the waiting list there. However, these rooms are usually reserved for visiting professors and academics. You can apply for an apartment at a university guest-house through the Foreign Students' Advisory Office. Again, you should make your application as soon as possible.
Notice boards: There are notice boards (Schwarze Bretter) in universities and many research institutions, usually to be found in canteens and other busy locations. They are often plastered over several layers deep with apartment notices and are accessible to all students and employees and cover a wide variety of needs. However, most advertisements are for single rooms in shared accommodation.
Student unions: The student unions (AStA/UstA) at some higher education institutions run student accommodation services which arrange private rooms. Students get the addresses of several landlords/landladies who have rooms available. The chances of getting a room are good, because each address is only given to a limited number of students per day. AstA and Student Services put up large notice boards where notices searching for or offering accommodation can be posted. You will also find notice boards in the department and the Mensa but these are usually covered with notices searching for rooms.