My driving teacher was a guy who did this. I dunno if he actually married them or if he had a prenup or what, but he would just swap them out for a new one every year or two. He kept telling me how great his life was, how he would get them to cook and clean for him him. I got a new teacher after a couple of lessons, it was too weird. I should have got a new one after the first lesson, but I was kinda fascinated.