Economy
Economy is a new gameplay mechanic added to Assassin's Creed II and is a major part of the game.
Function
Florins
Money, or Florins (f), are the most important part of the Assassin's Creed II's Economic System. You can obtain Florins by completing story missions, Assassination Contracts, upgrading your villa, looting treasure chests throughout Italy, or pickpocketing civilians. Obtaining Florins gives you a wide range of abilities. For instance, it gives you the ability to buy armor and weapons. Upgrading your armor and weapons can provide you with better resistance to attacks or give you better bonuses to do more damage. You can use your acquired Florins to hire people throughout Italy to distract or kill enemies. You can also buy medicine, poison, paintings, or pouches, as you see fit.
Armor and Weapons
Most armor and weapons in the game need to be bought from a Blacksmith. Exceptions include Altaïr's Armor, the Hidden Blades (provided by Leonardo da Vinci), and the first 2 swords Ezio uses. Aside from purchasing armor and weapons, they also sell ammunition and provide repairing services for broken armor.
Combat Skills
Training for long weapons, two-handed weapons and ranged weapons need to be bought with money. This is paid to the trainers at the Auditore Villa at Monteriggioni.
Auditore Family Villa
A prominent building in Monteriggioni, the Auditore Villa was built by Mario's great grandfather (Ezio's great, great grandfather). It features a large Assassin logo in a fountain near the stairs to the villa. The villa and the city of Monteriggioni are introduced to the player in a state of disrepair, with many buildings in poor condition. Mario explains that he has neither the time nor the money to fix up the place. The villa is not directly upgraded, but is cleaned up along with Monteriggioni as Ezio spends money on renovations and upgrades to the small city.
Any money spent on Monteriggioni increases its value. The city is able to earn more money as Ezio upgrades it. This money is available to Ezio in the chest behind where Claudia sits. Being the landlord of Monteriggioni, Ezio is entitled to discounts at the stores in the city.