Yeah...I am on the fence about ghosts...I'm with ℜ❀$eღud❧, birdsfreakmeout, Nervy Girl and B. I'm not sure what could be at play and I have never experienced ghosts or "uneasy feelings" even at old, abandoned places and while trying to be receptive to it. Heck, I have even visited cemeteries at night, and nothing, also attended a few ghost tours and again, nothing. Every orb I have captured on film can be attributed to dust, or a raindrop on my camera lens. It is fun to read about them though, hear ghost stories and think every little sound and sight out of the corner of our eye is a ghost, unwilling to attribute it to something more realistic or the laws of physics, events like the wind or a storm, because thinking it is a ghost is just more fun.
I do agree with others that living in an apartment, condo, or townhouse will definitely bring about some odd noises that you may have trouble with explaining away, at least initially. I had rattling windows in my condo. The issue? The caulking that sealed out the air was old and so were the windows, so any time there was any kind of gust, the windows would start to rattle. The air circulation coming through the air leaks would make some of my doors slam too, and I'd find pigeon feathers inside my home, because they would get through the cracked caulking. I had my windows replaced with impact windows and all that has stopped. I do hear whistling during gusty days but that's got more to do with the curves of the building that trap the wind than anything else.
I hear laughter sometimes that comes through the a/c vents, the noise of a vacuum cleaner coming through those same vents, stomping (kids running down the hallway), the sound of gurgling water from the pipes, and tapping on my window (scaffolding ropes hitting my window on windy days), as well as a scratching sound on the glass at night (pigeons' claws as they try to position themselves to sleep on the window sills). I sleep with a white noise machine and on occasion, I wake up and the sound is off, as if someone moved the switch. Not sure what is turning it off, but I guess it could have been a brief power surge or an overloading of the grid. My daughter used to say she could see angels/little children in our other place, and she would sing to them. Not too long after, she stopped talking about them and I never gave it much importance. I figured they were like imaginary friends for her. In my current place, shortly after my friend died, she said she saw someone watching us. Same thing after my dad died. I figured it gave her comfort and left it at that. I didn't dwell on it, nor did she. My sister thinks my parents' room is haunted because dad died there. I sleep in that same bed where he died and never had issues.
I am wondering if you may also have some air circulation issues that are causing doors to slam. When my a/c kicks on, sometimes, it will make doors open (if they are closed) or close (if they are open) due to the built up air pressure. I also wonder if you'd be thinking it's ghosts if your daughter hadn't mentioned it. I'm not trying to lessen your experiences or hers but they say you can cause things to happen in your mind with the power of suggestion. Maybe the kids at school have started talking about ghosts after seeing a ghost movie and they have her believing that every little thing that happens is a ghost. She could also be afraid of the dark and rather than admitting it, she could be blaming it on a ghost that is scaring her. She may also have been unhappy at the apartment and hoping you'd move. Regardless, I think the burning of sage cannot hurt, and the fact you're going to be moving to a new place may put these issues in the past, behind you. Enjoy your new home and best of luck!