I built a kit-car in the 80s. I started doing "just the odd bit" in the back room during the winter - until it escalated to the point where I actually had the entire bodywork assembled, for trial-run purposes. There just a single doorway to the outside world.
I had a chap knock the door trying to sell double-glazing. As I evaded buying anything off him, he tried "Do you need any patio doors?" I pointed out that the usual sliding doors and French windows just wouldn't be suitable. "What do you want then?" - "A one-piece, six-foot square, up-and-over." - I showed him the room with the full-size car in it and the small door out into the garden. "I will get you a quote!", he declared, but I never heard anything...
I often wonder what happened when he got back to the office with his 'lead'...?