Buddy of mine lived in a really old building (built in the early 1800s I believe) in a really old small town in Texas. His apartment was upstairs, businesses were downstairs, whole building was originally a small factory of some sort that had been remodeled for more modern purposes. There were some obvious "this wasn't originally an apartment" features, like a small door in his closet that seemed to lead to strange empty space between the walls, with no real reason for existing. Even when the door would randomly blow itself open with freezing cold air, you could sort of write that off as being due to remodels of old buildings, and not all the kinks of ventilation and stuff being quite worked out. That's kind of the explanation he gave to the strange noises he would hear coming out of there too. Also windows would always be open. Not windows he or his gf had opened, just random windows around the apartment. He would always close them, and then later find them open again. Seems like faulty latches that just come open over time, and not a huge deal.
Then he stayed home from work one day, and he heard the window unlatch. Not only did he hear that one latch fall open, but a second later he heard another the window unlatch, then another, one after the other, in order as if someone was walking through the living room unlatching windows as they went. Then all at once, each of the windows fell open. So he nope'd the fuck out of there for the day and came back that weekend to investigate. Things seemed fine, nothing weird happened for a while, then about a month later his gf experienced the same thing when she was there by herself. After a while they got used to it. Just weird windows.
Then the final nail in the coffin for that place was when they got a dog. The dog was a puppy, so was inherently happy, playful, always running around doing puppy stuff. Except when the door in the closet blew open, or the windows unlatched. Then the dog would stand completely still, focus its eyes on something that nobody else in the room could seem to see, and the dog's eyes would slowly track around the room, as if it was watching someone or something moving through the room. Nobody could ever figure out what the dog was looking at, and it only did this right after some other "ghost" stuff started happening. They moved out after this happened a few times.