Hate to do it, but...

I'd get the survey done if it's in your budget.
Several years back I had the neighbor of my rental want me to go 1/2 on replacing a fence.
I told him I wasn't paying for 1/2 of his new fence. He cited a rule in the twp that requires fences on property lines are joint ownership items.
When he bought the house, he didn't have a survey done, the fence was built by the previous owner and was 10' into a 14' alley. So as it turned out I wasn't his next door neighbor after all, and his fence wasn't on his property. His yard was 14' wide x 200' long, smaller than he thought.
I already knew this as the previous owner tried to have the alley closed and the property deeded to him. I fought it, because in the 70's, when the alley was created, my grand father lost 7' of the 14' alley and if they closed the alley, I wanted the 7' back.
Anyway, in the end he had to take down the fence that was obstructing the alley and the twp is exempt from it's own fence rule.