That's what I supposed (I am Italian myself) but it looks different from the French thing. From what I understand with "nuda proprietà" you buy the apartment but cannot use it until the person in residence dies or voluntarily leaves. But you the owner will not pay anything to the "tenant". So there is no extra spending even if the person using the place lives much longer than expected.

Well nuda proprietà is actually a bit more general a concept: it just means that one person has ownership and the other has all the other benefits. Remember when Berlusconi touted that as the solution to his conflict of interest?