What I loved about this place:
Maria Jose is a terrific host. She checked in on me several times via text, was attentive and kind. The apartment is really lovely, in an exciting area of town - really central. It's the kind of place that you stay in and imagine as your own home, or certainly imagine life as a local. The day bed is a nice touch, and the wifi was good - I had to get a lot of work done on the first day.

The downsides: There's a loud club below and there are a few sex workers up and down Ballesta. That being said, it didn't feel unsafe.
Also the advertisement is for LastMinute50eur, I booked it quickly and upon finalising realised it was €62/night. The price should match the listing.

I'd still recommend it - Justica is a great part of Madrid, and the stay was simple and nice.