I had an amazing time at Felipe his apartment. It's really close to all the major sights. You can walk to Sol in 10-15 min. And on a sunday it's next to Mercado el Rastro, definitely a recommendation if you are in Madrid on a sunday. The place was really clean and Felipe is really helpful, he will reply to you almost instantly. He also gave really clear directions on how to get to the apt from the airport.
I didn't meet Felipe in person, but his mom let me in and she was a really kind lady. If you are thinking about staying in a apartment that is central and clean, stop to look any further and book this one!