Buying a house with life tenant - how to price?

[Maxym Le Deux]

Hello everyone,

We are buying our landlord's house (2 floors) we both live here on separate floors. As part of the agreement, we will let our landlord stay for life. We will not be able to sell or rent the space our landlord lives in. He is around 68 so that can be another 30 years before we have full control and value. 

Is there any special way to price the property?