On the 15th of Adar, special money-changers were established to aid acquisition of the Half-Shekel for its donation to the Temple: Megillah 29b
On the 25th of Adar, special money-changers were established in the Temple itself to aid acquisition of the Half-Shekel for its donation to the Temple: Megillah 29b
How often did money-changers set up shop in urban and rural areas: Bava Metzia 52b