[drew]

Hi Saul,
Depends whether it is agricultural land, land which could be built on, "just" garden attached to his house... make an appointment and go speak with your local Notaire. Depending on what the bit of land is designated (and you may want to speak to the Mairie first to try and establish that) there's probably a "rule of thumb" price which the Notaire will know. Then offer a bit less.
Thanks a lots