In Austria, you can get a single appartment for 400-600€. A room in a shared flat can be even cheaper. So with 100000$ you can indeed survive for 10 years or live comfortably for 5 years. This mostly applies to Germany as well, although certain cities (like Munich) are rather expensive.
Most smaller university cities in Germany and Austria are very inexpensive. Leipzig, Heidelberg, Kassel, Münster for example. Even Vienna or Berlin are not too bad if you are okay living further out and with roommates.
Eh, I wouldn’t say very few. Depends on the subject and many merely require that you learn German within a year of attending. This design school, for example, is mostly in English: