Cosimo succeeded his father Giovanni in 1429 and became director of the family's bank
The Medici Bank brought lots of wealth, making Florence wealthier with it
The bank was created in Florence because the Medici's lived there. It was created during the Renaissance because during the Renaissance people started to think of many new ideas, this being one of them
There were also branches of the bank in different parts of Europe. Branches that were added while Cosimo was in charge include: London, Geneva, Bruges, Avignon, Milan, and then later Geneva was transferred to Lyon