What's actually in your shed or garage? A lawnmower you never use (in which case you should go back to point 4)? A rotting pair of wooden ladders? Some half-finished DIY project that you always meant to go back to but never actually have? It probably isn't your car, because that's either on your driveway or in front of your house. So, what is in your outhouse building, really?
If you didn't guess the answer, it's storage. People are constantly on the lookout for storage space. Sometimes it's for the long term, and sometimes it's just for a while, for example people who are in the middle of moving to a new house and need somewhere to place their stuff until it's ready. Like your parking space, your shed or garage is something you already have, waiting to be deployed as a money-making solution.