My (fairly spry) 90 year-old father and I will be visiting Florence in June and would appreciate suggestions of hotels that would be comfortable, well-located to the main sights, and without multiple flights of stairs to negotiate.
Just ask the hotel before you book if they have an elevator. Our experience is that most hotels, even small ones have elevators.
Hotel Casci is very inviting and comfortable. It has air conditioning, a large elevator, modern bathrooms and very friendly staff (family owned and operated). It is on Via Cavour just around the corner from Mercato Centrale and the San Lorenzo market. It's an easy 5-7 minute stroll to the Duomo.