This place is very well located and quite cheap. It’s an older apartment and rather dark, but it was reasonably clean. It’s a hostel setup and you will be staying with other guests in the apartment. You’ll have a hard time finding an acceptable place to stay in central Madrid for this price!
A couple issues: The room doors don’t lock and the wardrobe lock is not really secure so only bring what you won’t worry about. One issue with this room is that the outside hall light shone right in the window whenever anyone was climbing the stairs to other apartments. (The small window looks out onto the breezeway.)