Rent this place if you really have a low budget and can't afford a decent hotel/hostel in Madrid. The only comfort of the place is that it is close to the subway station, which anyways takes 20 min to reach to the city center.
Teresa was a kind lady, she tried to help us as much as she could do. However, don't rent this place with expectations. There are 2 cats at the flat therefore there are cat hairs visible even on the plates to eat. The cleaning of the room was not properly done, we found a ear stick (probably used by the previous tenant) on the floor. The big plus of this place was the mini-fridge that you are provided in your room. Consider this place just as somehwere safe to sleep, nothing more.