Miguel Angel was abroad working when we visited Madrid for a week. His mother Ester hosted us. The apartment is literally 2 mins walk from Plaza Major, with plenty of shops for food or cheap eats around. Retiro park is around a 20 min walk away through historic part of Madrid.
The room has space enough for a bed and place to store luggage but not much more. Even though you are in the center of the, the room is away from the street and totally quiet at night. For the price you can't complain though.
Ester was an incredibly kind host. She served a simple but filling breakfast from 8am-10am every day (toast, ham, peanut butter, chocolate spread, jams, small cake or cookie, yoghurt and coffee). She was very nice and friendly company to have, with a "mi casa es tu casa" approach to hosting.
If you are looking for a central location on a budget, this place is great.