The ErVin house is just perfect.
Clean, bright, well equipped. Situated in a very nice and local (not so touristic) neighborhood: 10 minutes walk from the train station SMN, 10 minutes walk from the river and you can also reach by walk the main touristic attractions. I personally enjoyed the walk along the river to get home every day. Nice restaurants and bars around.
Fabiola is super kind and welcoming, she's always willing to give you advice as a local.
I stayed in different flats in Florence. This is definitely my favorite. I will definitely go back.