My friend and I stayed at Cristina's place for 5 nights. We paid 25 dollars per person for one single room and I have to be honest it is even cheaper than any hostel in the center city. Price is unbeatable.
But we indeed encounter few things that other reviewers also mentioned in the review. Please remember you get what you are paying for.
1.there are other few guests staying. I usually donn't find it is a big problem if they know to keep quiet. But one night, 2 girls from the other room got back around 3 am and couldn't use their key to open the door. They buzzed the door.they were loud after friend let them in.maybe the host can think of setting the rule that all tenants should keep quiet after 12am?
2. Heating is another issue. The ac needed to be controlled under 23 which was impossible for a cold night in Madrid. The temperature are different in every room. We feel really cold after we know we need to keep the temperature down to 23 and we already use 2 comforters. Anyway we left right after that night. Maybe the host can consider to leave small heater in each room. I realize all the other airbnb host does that.
If you aren't concerned about a/c and other tenants' issues, this is a good place too stay