Tell him to prove the boundary dispute by providing a certified copy of the land survey.
You don’t need to pay for a second survey. If the first survey was forged, the neighbor won’t be able to provide a certified copy.
If he provides a certified copy of the survey, and it shows the boundaries are not what you thought, you should go to the planning commission, or whatever office provides plot maps for your neighborhood, and see if the numbers match.
Ask a surveyor for help in confirming the survey, if necessary. It’ll cost less than $100 for this service. You’re not asking for a full-on survey, just verification of what’s been provided by the neighbor.
Meantime, do nothing until the neighbor provides verifiable proof of his claim.
In the event that the neighbor’s claim is provable and legitimate, then all of the sudden …the fence belongs to the NEIGHBOR, not YOU…!
In many places, both neighbors are required to share the costs of fence construction, if its on a boundary line. Just saying.
As an aside, this is what I would tell the neighbor:
"If your survey is correct, Mr. Neighbor, then this fence belongs to YOU.
Since this fence belongs to you, you can do whatever you want with the fence. (evil laugh inserted here)
Meantime, if you remove the fence, I will sue you for half the cost to build a new one on the property line. And I’m not putting up a flimsy wooden fence. We’ll be installing concrete block. I’m sure your half of the fence won’t be more than about six thousand dollars, after all is said and done.
So, Mr. Neighbor, you are going to pay for the demolition of your existing fence, and then you are going to pay for half the costs of “our” new block wall. Let me know when you want to start construction."
I’m betting the seller will all of the sudden be quite content with the fence as it stands. Meantime the fence could be ‘grandfathered in’ at the current location, depending on how long it’s been there, and as importantly, ‘whom’ built the fence that far into the neighbor’s property in the first place.
In the event the survey is correct, the neighbor ‘could’ threaten to build a new fence on the “correct” property line, and demand the YOU pay for half. It could go both ways.
The neighbor could build a fence on the property line, and then put the ugly side facing your house. Whoops. Worse, he would try to make you pay for ‘half’ of ‘that.’
Meantime again, I’m betting a former owner of your neighbor’s property built the fence on his side of the property line, so he wouldn’t have to get permission from the previous neighbor about its style, construction, and appearance. I don’t know.
So, if the fence IS inside the neighbor’s property line, then the neighbor can go suck eggs, and/or remove the fence at his own cost, and then figure out how he’s going to pay for the new one on the property line.
Hope that helps.