Gone is the old way of receiving your weapons and upgrades: listening to some old man preach about how everything is permitted and nothing is true, and then having him restablish your rank in the Assassins Guild. Now though, since there was an economic system in this period of history, all of your upgrades will be bought from a blacksmith, including most of your ammo (Throwing knifes, smoke bombs, and bullets). To gain money, one must complete quests, pickpocket (anyone you see will have money), or find these chests that are dying to be looted.
Ultimately this system gives a much more realistic feel to Ezios arsnal. There are other shops too, including a tailor for those wanting to change out of those blood stained-white robes. I chose some ventian amber, until I acquired Altairs armor (which looks nothing like what Altair wore) (whoops! Spoiled)
Also, to add to the historical accuracy, there is a painter shop where all the 'latest' works can be purchased to boost the cities monetary value. To top it all off, there is a certain city where your uncle Mario lives (yes there is an awesome Nintendo reference) that needs renovating. By spending money to help re-build the town, more tourists come to spend money, thus increasing your income (your uncle owns the place it seems) and you also get discounts from local stores that you helped out.