They make those get ups, actually see the adds on the DIY site, as far as I know they are not UL listed or any other kind of approval, certainly doesn't doesn't even come close to the intent of the code and didn't see anything in the instructions that would suggest that this would be an acceptable idea. If a guy was on the up and up with me as a landlord I might even participate with installing a legal circuit, a new wire to the panel with the right breaker. I might even feel better about that than hooking something on an existing 120V circuit especially if its older.