My boyfriend and I stayed with Francesco for a few nights whilst visiting Madrid.
The room is basic (it has a bed) and the bathroom is small but perfectly functional (however if you are very tall - which sadly I am not - you may find the tiny shower challenging!). The space was small but adequate to our needs. We tend to need somewhere to sleep and have a shower since we like exploring in the day. If that is what you want then this will do you fine.
The flat is very central and within 15-20 min walk distance to the furthest point of interest in the city. However, if you are not much of a walker then there is a metro station within a minute from the flat.
Francesco is a charming host and takes a great interest in his guest. He clearly loves and knows his city and provided us with a local map, tips on where to go and also special bars/ restaurants to visit.