A Preliminary Contract or "Compromis de Vente" is signed at the estate agent's or notary's office. This agreement is subject to "conditions suspensives" for example: the obtaining of a mortgage, planning permission etc. The estate agent will explain in detail the importance and contents of this document.
A deposit must be made on signature of the Preliminary Contract at the estate agent or the notary, usually 10% of the net purchase price.
You have 7 days cooling-off period to cancel the Preliminary Contract without a penalty. After this period the "Compromis de Vente" becomes binding on both parties, you and the vendor.
Deed of sale or "Acte de Vente": this official document prepared by a notary completes your purchase.
The balance of the French property purchase price plus notary fees, Land Registry fees, taxes etc. must be paid on signature of the Deed of sale.