>>2429051lower the further away from a city you are. i wouldn't camp in an abandoned building in a city, almost certainly going to be druggies and homeless there. they are attracted to the shelter and privacy of abandoned buildings. if it is outside of a big city, reasonably difficult to get to, and hidden, you should be fine.
pic related is the industrial wasteland where i took most of my photos.
20 min walk from a town and homeless druggies, only just outside the town but behind a fence or two and reasonably difficult to access, you either have to cross a dodgy stream (littered with those blue chemical barrels) and climb through a hole in a fence, or climb a hill & find the secret entrance (which used to be locked).
plenty of evidence of people being there before me but not for a long time. probably when it was more open.
you can choose your time wisely too, bad weather forces the homeless indoors, so if the weather is a little bad, much less likely to be people outdoors in industrial wasteland.