Boundary survey is a must. It is less than a survey that marks out everything on your property(house,garage,shed,septic).It just marks the corner pins,and usually they place a few stakes along the line. I had trouble being able to measure from the corner pins to middle property stake,so I had the surveyor come back and put stakes every 10 feet.No question where the line was,but guess what....the neighbor still mowed past the stakes. Only a fence held my neighbor back.
A boundary survey is your best option,and you can do one side or all sides.Once you have it done your neighbor can do his own survey to confirm or dispute.If he does a survey and it does not match then the 2 surveyors are required to hash it out,and figure out why there is a difference. Your neigbor can not just say," I don't agree with your survey." though as mine did they will try. Just ignore.
Legal is where its at not opinions,or going out with a tape measure and metal detector. I added extra stakes so no one could say my fence was off by a few feet or inches.
I know what you mean about the funny feeling you get when you see a neighbor on your land.I got itand I am sure my neighbor gets it too.I waited 2 years after the survey for my neighbor to do one,but after 2 years of just mouth runs I put up my fence just inside those stakes. I feel bad that the survey did not match what my neighbor felt was right.All I really wanted was to know where the property line was so I could put up my fence.
Any future house I buy will get a survey done.Might even ask the sellers to do it or split the cost. The mortgage survey I learned is legally binding-it is a joke.All fencing companies I contacted would not use the mortgage survey.They said to get a REAL survey.
Best wishes!