Hello Peter,
Good to start the conversation. My flat is in a house that I share with two neighbours. I am on the first floor, there is a flat on the ground floor and one on the second floor. We all own the freehold to the house.
Up until a year ago I had a lot of problems with my neighbours, particularly the downstairs neighbour complained as guests would ring their bell all the time amongst other things. There was also a problem with guests staying in the front garden, which is shared by all of us. Additionally there was the issue of security.
It was all resolved by talking to them, and most importantly they actually made suggestions to my listing and description. The key was that I had described my flat as being on the first floor. For those in the US the first floor means ground floor! My upstairs neighbour is a writer, so he then proposed changes to the text, actually explaining that it is up two flights of stairs! In addition there is no access to the garden for guests to sit in and I have very clear guidelines on locking the front door.
And now there are now problems anymore. I do keep my guests posted on who arrives, where from and what the purpose is so that they are not surprised if they see someone in the garden. Equally I tell my guests about the neighbours, so all know roughly who is who.
And I still ask my neighbours each time to let me know if anything bothers them.