French Inheritance Tax Question

Hi,

I'm planning to buy a house in France to which I can retire.  A friend will, at some point in the future, also move out and retire to this property.

I'm unaware of the situation regards inheritance taxation in France, as when I eventually shuffle off I don't want my friend stung with an enormous tax bill, and possibly even having to sell his own retirement home to pay for it.

Right now I can see a couple of options, unless French law presents additional options...

1) Put 50% of the house in his name when I buy it, but what then happens when one of us passes away?
2) Slowly transfer ownership of the house to him until he owns 100% of it, but what then happens if he passes away before I do?

The sort of property I'm looking to buy would be around €100,000 or so.  Can somebody advise me please on this taxation matter?

Many thanks