found a closet in my apartment building full of wires and stuff. put a piece of tape on the door in a subtle way. left it alone for 2 months. tape was undisturbed. no one ever goes in there, evidently.

Got a laptop. Put XMRig on it, hooked it up to my neighbors wifi and the outlet in the closet. Turned it on. Fan is loud but it echoes and sounds just like the central AC running.

Free money to the tune of 0.60 a day