[Nodraak]

This sounds very illegal. From what I know, in France the notice period is 1 month if it is "meublé", or 3 months if the appartment is empty.

Edit: actually, I just checked and that's for tenants. If the landlord wants to break the contract to sell the property, it's 3 months for "meublé", 6 months otherwise.

[guerby]

Yes it's illegal in France, here is the official documentation:

https://www.service-public.fr/particuliers/vosdroits/F929

3 to 6 month with certified letter before the sale, and can only happen at lease renewal dates (every 3 years).