When I lived with my folks I grew. They didn't have a clue about it either. It was 100% stealth and I did it for 2yrs until I moved out. They never knew.

What I had, was a room in the basemeent. I had this walk-in closet, and inside the walk-in closet, was a crawl space door that was under the stairs. I made a very small cab., only about 2ft in height, rigged my lights in there, and hid all of the wires.