you live in an apartment building.
thats alot of people who could potentially be involved in it
im going to assume there are other residential buildings and houses as well in the area, along with possible businesses.
so thats a lot of potential people he could be looking into.
you can two ways with it:
ignore it, and live your life
call the police and tell them and make sure he is legally allowed to be there and that he is who he actually says he is,
I have no clue how private investigators actually work, but i would probably just ignore it.
I wouldnt call po po if my life depended on it!
Talk to a few neighbors, make the mf'er go on his way!
I think I would go out and have a coffee with him, maybe go out there after you burn one, I would mess with him untill he was gone, bawahahahahahaha!
no one gonna hang around my place and make me nervious,,,,,,,Im gonna make him nervious!
Peace