Moncho's place locates near Madrid main train station. With Línea Exprés (the express bus; line 203; Atocha railway station <-> Airport), you can easily arrive at Moncho's apartment. Besides that, we simply use Uber for other short transportation needs because our visit was mainly in the City Center. See https://travel4apurpose.blogspot.com/2019/03/3-day-travel-itinerary-in-madrid.html for details.