Mons is located in Belgium, check with the appropriate consulate or embassy in your country to find out if you will need a visa to visit Belgium, especially for an extended period of time. Some countries have extremely detailed and complicated entry/departure laws and treat visits of a week or two very differently from longer stays.
Nothing in particular in Belgium, no need to get many vaccines before entering the country. You can check it on the website of the world health organization. Of course, like elsewhere you will need travel insurance.
The currency in Mons is the Euros, you can pay cash or by using debit/credit card. There is enough atm to withdraw money in the town and the majority of businesses accept payment by card.
Useful Phone Numbers
100 Emergency medical service and firefighters
112 European telephone number in case of accident or aggression
101 Federal Police – Appeal Number for Road Accidents Without Injuries
105 Red Cross – Disaster and Disaster Assistance and Response
+32 65 97 9000 Police Mons
+32 (0) 65 33 55 80 Main Office