If we lose the keys at our Paris VRBO, we'll be charged five-hundred Euros. In dollars, that's... a lot, especially since I can get a key duplicated at K-Mart for a dollar.
But laws in France are different. Government permits are required, a process which sounds like going to the DMV on a really bad day. Certain keys could take ten days to copy.
One American writer living in Paris laments that if he wants a duplicate key – not the even pricier services of a locksmith – he'll need to provide the company with a copy of his passport, his electric bill, and a sworn statement that the key is for his own home, all sent by signature-required registered mail.
In the building where we're staying, there's an additional set of rules that requires the entire lock to be changed if a key is lost.
So check. And double check. And then check one more time before you leave.