Cardiff is the capital of Wales and it is a large centre for tourism with more than 18 million visitors flocking there each year. Cardiff is the home of the Millennium Stadium, Cardiff City Stadium, SWALEC Stadium and Cardiff International Sports Stadium (not to mention several other smaller sporting venues) which means it is the place to be for sports fans. Throughout Cardiff there are self storage facilities that people can rent out if they need somewhere to store their possessions.
If you have a garage that is safely locked and empty you could be renting it out to people looking for a cheaper storage option, and charge around £75 per month for yours.