Finding a flat in Prague is not difficult at all. There is an agency for Erasmus students that provides shared flats, which is a good way to avoid scams. In Prague, rent is around 400 euros per month to live close to the city center and all you need to do is to find other roommates and sign the contract. Otherwise, some universities offer cheaper accommodation in the dormitories but it is often far away from the center and less comfortable.
As a student in Prague, life is super easy ! The city is not only cheap and beautiful, it is also a great place for students. You can find cheap restaurants from all over the world and the city is famous for its nightlife : there are many bars and Erasmus parties almost every day ! Some clubs are amazing - much better than in Paris for sure - like EPIC if you like electro music. Last but not least, you can travel easily as trains are very cheap. For example, it takes 4 hours to go to Vienna or Berlin, and 7 hours to go to Budapest. So you won't get bored during your week ends...