I am looking for an inexpensive hotel either close to the airport or within walking distance of the main train station in Munich. I need to stay one night since my flight the next day doesn't allow for me to arrive the day of my flight. Any suggestions? Perferably if the hotel is by the airport you also know how to get back and forth between the airport and the hotel.
If you are going to the airport from downtown you really don't need to be near the Hbf, just one of the S-Bahn station under the city (eg, Marienplatz). Trains go either through these other stations after the Hbf on the way to the airport (S8) or on the way to the Hbf, then to the airport. For a list of hotels near the Bahnhof or Marienplatz, see the list at the bottom of my webpage, here. I also have several places shown in Freising. It's a 20 minute trip by bus from the Freising Bahnhof to the airport.
I stayed at Hotel Locarno last Octoberfest. It is right on one of the exits from the HBF. Very convenient location and reasonable rates.
Warning: In comparing rates for hotels in Munich, look for the words "Frühstück ist inbegriffen" or "... inclusive". Most German hotels include breakfast in your room rates; some omit it to make their rates appear artificially low. If you are leaving for the airport so early that you won't have time to eat, then it might be a plus, but I really like having a nice breakfast before I start.