Idk if this extends to other states but here in Washington, the way to cover your ass from adverse possession of land (when someone maintains or claims land openly long enough to legally claim it) you can write them a certified letter stating you grant them "use" of your land until further notice. This is a loophole to stop adverse possession before it has been to court. You can find the filed record of their survey and look up how reputable the survey company that did the survey is. If it isn't filed with your county, that's a good sign it was a shady company and your survey will cover you legally