Amsterdam is quite a popular city among tourists, so we advice to book your accommodation as soon as possible. Here are some suggestions for affordable hostels close to both Science Park and Roeterseiland campus:
Alternatively it is possible to find cheaper accommodations in the nearby towns of Almere or Weesp. Both have direct train connections (Sprinter) to Science Park as well as the Muiderpoortstation, which is within walking distance from the Roeterseiland campus (ca 20 minutes).