Madrid hostels

Matteo, go to www.booking.com and look for an affordable hostel or hotel in the central Madrid area.
The metro in Madrid is very easy to manipulate.

Near the airport no, but near the Cercanias train (5 min walk) that will take you there yes. It will take you 30 min. to get to the airport, keeping in mind the train leaves every 30 min. In other cities you would pay an arm and a leg to stay within 100 meter of a worldclass museum, but Lori, @peregrina2000 recommende Hostal Bruna. 35-40 Euros a night, 5 min walk up from Atocha, and 100 meters from the Prado whih is all you will want to walk to and from it after visiting its marble floors post-camino. I cannot beging to imagine what that flat is worth! Hello retirement! A lovely family runs it, it's clean, AC'd, and has an ELEVATOR! ;0)