AFAIK no listing agency/company has any obligation to list only legal apartments. If a company chooses to do so I would expect it to say so.

I sympathize with wanting a VRBO-type apartment, especially traveling with family, but have come around to thinking that it's not in Paris' best interest. Or that of Venice, Manhattan, similar desirable cities with a concentrated core.

Rome, London, Boston, maybe.

'they have high standards so they could indeed check on the legality'

Like François Fillion has high standards and therefore abides by the law ? I'd say the probability of having a high end apt whihc is legal is lower than a 'normal' apt.

In a normal apt you have normal people who may want the additional revenue of a rental. In high end apartments, owners (yes, not renters, faux ami) would not want to share their apt with tourists would they ? They would simply buy it and rent it all year round...