I have stayed 3 months in Jay’s flat. It’s very well located, bright, warm and has all you need. Ideal too explore Madrid and the museums around. It’s not that new like it looks in the photos but is still cozy and everything works fine specially for a short stay.
You are going ti share the flat with more people since there are two other rooms in the flat and your whole experience might depend on the other guests too. I had an incident with a guest once and I was expecting that Jay and his co-host would have put more thought in their communication between them & I but the issue was solved anyway. Jay does not live in Madrid but he will try to help if you contact him.