If it's a newer model (2001 onwards) with multiplex wiring and there's any
sign of damp in the passenger footwell then walk away. A work colleague
bought a 406 HDI Exectutive, the very next day it clapped out on him as the
BSI (which sits under the fusebox and conveniently catches any water coming
down the wiring harness towards it and also off the base of the windscreen
if it has the slightest leak) was waterlogged and needed replacing. It took
the local dealer 3 weeks to get the car going again after replacing the BSI
and reprogramming it to talk to all the bits of the car such as cruise
control, aircon etc.

Chris