Domus 19 is a great place to stay. It's clean and cosy with lots of lovely details around the building. Loads of plants and books as well as a beautiful terrace with a great view over the city. Raimondo is super helpful and communicative, doing everything he can to make your stay a good one.
The location is perfect - a genuine, local neighbourhood without the herds of tourists but still super central and a short walk to the historic centre (in-fact, it is still in the centro storico, just on the edge). Tons of great bars, cafes and shops near by and just around the corner from the river.
Highly recommend Domus for a comfortable, affordable and local stay in Florence!