Hi Jerome,
Assuming you are looking to retire to France. Here are the requirements.
A couple, 65 years and older, must have sufficient financial funds of around 1,400 EUR a month. Keep in mind, the amounts change depending where you are looking to settle.
Non-EU citizens retiring to France need a residence permit to enter France. Also, you cannot get a residence permit card without obtaining a long-stay visa first.
In terms of cost of living, budget of around 2,500 EUR a month will cover a couple living well and running an apartment.
Waq