@Christine49, @Robert52,
Sorry if I am going to be the person to pour cold water on this but let's go!
In France regulation for short term rental is clear and strict (even more since the huge increase of airbnb). First of all, only owners can rent. Subletting is totally forbidden except if you have the formal and writen agreement of the owner, in all case your are not allowed to make money up to the rent you pay to the owner. Then it depends of the status of the housing: is it your main home or your second home?
If it's your main home you can rent it as an entire home or just a private room for a maximum of 120 days/year. Up to 120 days you need to ask for a touristic license at the mayor urbanistic department.
If it's your second home, normally even to rent 2 weeks you need a touristic license. And you need to know if it's located in one of the 200 municipality specified by the french law as tense regarding housing. If not, great! to obtain a touristic license is easy, just have to filled the official form and that's all. If not, problem! above all in big cities like Paris. Each town have is own rules to reach the same purpose: to compensate the fact that while your short term rent your house, normal working people can't rent it with a long term lease. In some town you will have to pay a monetary compensation for each square meter on short term rental, in others you can't rent if you don't put the same number of square meters on the long term rental market (so if you want to rent on airbnb a 30m² studio, you have to rent on long term rental another of 30m²). Many french big towns have now special squads to fight against illegal short term rental. A new law, confirmed by the Parliament, not yet by Senate, will sue illegal renters with a 25.000€ fine, inmediate eviction for tenants, etc.
After that you have to pay taxes: the first is the touristic occupancy tax which is due per night and per person up to 18 years old, each town have his own amount and modality. And all the income have to be declared to tax office, you will have an automatical 50% tax allowance, even if you are not french.
That is just a little resume of what french regulation and formalities are. Even for french people it's difficult to understand everything.
@Christine49, feel free to ask me if you want some precision about a specific point.
Cheers