Can I build whatever I want?
In France, every city has a « Plan Local d’Urbanisme », usually called PLU. This document is related to a map that organizes the land in different areas, such as « patrimony city center », « industrial area », « commercial area », « natural landscapes », « agriculture lands »… Absolutely all the rules about the height, the type, the use, the materials, the distances, the surfaces that are allowed and forbidden are described. As soon as you find a land, in order to collect all these rules, you can :
Meet an Architect that will advise you both on the rules applied to your land through his own experience and through a «Certificat d’Urbanisme». He will help you to find the good balance between your project, your budget and the potential of the land.
Meet the « Service Urbanisme » at the city hall of that specific area to get the informations through their services. They usually recommend you to ask for a « Certificat d’Urbanisme» too.
Read the PLU by yourself. It is tough but it is possible.