The cost of accommodation in Vienna is quite high, and these expenses will make up the lion's share of your travel budget. Nevertheless, it is possible to find a suitable option even with very modest means.
An approximation of living in Vienna:
A stay in five-star hotels in the city will cost on average 180-300 EUR per night;
4-star hotels in Vienna can be had for 90-140 EUR;
3-star hotels will open their doors for 50-90 EUR;
in small hotels 2 stars, located at a distance of 1-2 km from the city center can be accommodated for 20-38 EUR per night (usually without breakfast);
and finally, accommodation in Vienna is quite inexpensive with local hostels. As an example you can offer a&t Holiday Hostel, which offers rooms for 2-6 people for 13 EUR per night (without breakfast), or Hütteldorf, where a bed will cost 17 EUR with breakfast. The hostels have a shared kitchen where you can cook for yourself.