When did they start?
They started in the 1100s in Europe. This century is called the "12th century renaissance" by some historians, because it was the beginning of market capitalism in Europe.
Towns like Ypres and Ghent in Belgium would hold huge market fairs, and Italian jews would come and set up "bancos" (which means "bench") to lend people money.
Jews did this, of course, because Christians were not allowed to lend money. This gave rise to a lot of the stereotypes some people still have about Jews.