Neighbor's Tree's Roots Growing On Property

[Alex Huang]

Walked through a property today. 

One point of concern is a tree that is in the neighbor's yard. The tree is very old and healthy, but its roots are MASSIVE and are growing near / under the foundation of the house (monolithic slab). The original fear was that the foundation of the house was a mess, but an inspector looked and felt pretty certain that the settlement is due to these tree roots.

The obvious option is to open a dialogue with the neighbor and to see if we can have this tree removed (50/50 split on cost, whatever), but in the event that this neighbor has no interest in helping, what are my options?