Xabier's place was exactly as described and perfect for our group of 4. We met with Xabier's mother as Xabier was traveling on the day we arrived. She was wonderful! She showed us around the apartment, went with us to show us the parking and provided some helpful tips and things to do in our brief time in Bilbao.
The apartment is up a hill (about 2 blocks long) on a dead end street. This made it easier to load/unload the car before parking as there wasn't much vehicular traffic down the street. The apartment is up a small flight of stairs, however, there is a small elevator available to bring luggage/heavy items to the apartment that allows you to avoid using them. This was really convenient as we had some heavy luggage with us that would have been difficult to carry up the steps.
Everything in the apartment was great for us. It was sparkling clean. The parking space was really important because of the lack of street parking available in the city. Please note that there are no shades or blinds in the master bathroom. This was a little weird but the bathroom faces a wall so no one can actually see into the apartment. Overall we were really happy we chose to stay here and would recommend anyone to stay here!