Living in Prague if fun and relatively inexpensive. (Here is a nice page giving you an idea about living costs.) There are many options where to stay. Students of the CEVRO Institute may use all dorms in a pool of accommodation facilities in Prague, which is owned by Prague universities and open for all university students. Students may also wish to arrange their own housing in Prague through many commercial agencies.
Or try MyFlatshare. Housing is not provided directly, but you may use their website to search for available flats, and even offer a room if you’re looking for a flatmate.