In the late '70's as a new PPL, I used to rent a seemingly unused C 172, which was based at Toronto International Airport (YYZ) (back when light aircraft were tolerated there). This 172 was decently equipped, and always available, the fellow who owned it was entirely agreeable to about any use of it, and it was available at a very attractive rental - around $35 per hour, if I recall. I always wondered how he made a buck with that plane.
He also had a C-310 and C-337, which were said to be available for rent, but were much less available. I never did manage to rent any time on either for training toward a multi rating. It turned out that these two aircraft were operated in harmony, smuggling up from the United States. They would be flown over lake Erie, in an area which I suppose had poor primary radar coverage. One TXP off would cross paths with the other, and swap TXP codes, while the smuggler would then turn his TXP off, and sneak off to a no customs landing site. I don't know exactly how they were caught, but I heard they were. I suppose a sharp customs agent realized that a C-310 filed the flight plan, but a C-337 arrived on it! The 172 was just a smokescreen....