We stayed at Sergio's apartment over the Easter Holiday. The place was spacious, clean and convenient, and its proximity to a number of metro stations meant that it was easy to get anywhere we wanted to go.
Sergio also helped us promptly address some minor issues we had with heating, and messaged me several times to ensure that the problem had been solved, which I found reassuring and considerate. I would definitely recommend him as a host to anyone looking for an affordable and pleasant stay in Madrid.