What is the number of existing- apartment and house sales in each French department?
Data about residential and other property sales are available at https://app.dvf.etalab.gouv.fr/.
Cerema also provides data (DVF and DV3F databases) : https://datafoncier.cerema.fr/.
See also the methodological notes (in French) about the estimation of the number of existing dwellings in all of France.
To English page : Property Market in France since 1200
To English FAQs
To French home page "Le marché immobilier depuis 1200"
To French FAQs
About the "tunnel" (in English)