We will be arriving Florence next May 10, 2020 from Naples by train and need accommodations for 1 night. We want something close enough to take a bus to the major sites such as David and Duomo etc (we will only be in Florence for 1 day/night before heading to Chianti area. Our budget is limited so can't afford anything over $150 USD per night. Can you help?
Florence is very compact. Unless there are health issues that prevent you from walking you will not need to bus anywhere.
The Accademia where the statue of David is located is a 7-10 minute stroll to the Duomo.
As far as where to stay see if you can book at Casa Howard.
The train station is itself within easy walking distance of many of the hotels in Rick's books, as well as the Duomo, David, Uffizi, etc. The part of Florence in which most tourists are interested is indeed compact, and just a few blocks from the train station.
Check out Rick's books for recommendations; there is a wide range of prices for hotels in the "centro storico" (historic center.)