Rebecca states that although all Families own banks, most of these banks are owned by the Pazzi family and that breaking into them (By silencing the guards) will be worth your time.
Banks will always contain 2 chests or one codex page. Also, the money you get from the chest vary greatly, reaching rewards of 100, to over 1000 florins.
Trivia
It is possible, In Florence and Tuscany, to create a small civil war via Banks. To do this you need to come across a Pazzi owned bankFile:Pazzi.jpgA group of Pazzi, guarding their Bank(The soldiers are dressed in Pazzi Red, Not Medici Yellow) and either attract Medici guards to the Pazzi ones or attract the Pazzi guards to a Medici Patrol (By angering the guards and getting them to follow you.) Just lead the idiots to each other and watch them brawl. On a rare occurence, a guard may still target you rather than his other enemies, just silence him and keep your distance. If you want to have even more fun; Invite a few Mercs or Thieves into the brawl.
If you decide to invest in a well for your villa, you will notice that you can actually go down the well and survive, unlike others in Florence and their cities, beneath the well there will be 2 chests, and if you invest in a mine just north of the city wall, you can go into the mine, there will be 2 chests of florins waiting for you to collect. There will also be 2 chests in Ezio's room, the top floor of the villa. These chests, being rare, unfortunatley only contain 200-600 florins.
The amount of florins in each chest increase with every new city the player travels to, probably due to the increasing cost of weapons and armour.
