We enjoyed our stay at Caroline / Paul's flat in Vienna. This is a one bathroom and one bedroom flat. The toilet (no sink) is in one room and the shower/bath and sink are in another room across the flat. This flat is best for 1-2 people. The couch in the common area converts to a bed. This is called a second bedroom, it can become private if all doors are closed.
Paul was a great host, the check-in was smooth and he gave us a good restaurant recommendation.