We stayed at Giulia's place for 3d & 2 nights. We've been using air b&b since we started travelling in Europe. Giulia is one of those hosts that you can say "thank God for Air BnB." She's such an amazing host, room was very clean (more than our expectation). And she gave us the information like how locals really know the place.
The apartment is on the 5th floor, but accessible via an elevator. You have to take the bus going to the central market and trains, but don't worry the bus station is a minute walk.
Don't miss Florence, the place is stunning and its food.
Needless to say, I would highly recommend this host.