My idea of a walk on the wild side is to not lock the door into the house from the garage. But the other doors are locked.
We have owned several houses throughout the years, and we always have the locks changed as soon as we take possession. We also always change the garage code.
Even though you are buying from perfectly nice people, you never know how many keys are out there somewhere.
Just think — you could come home to find a stranger drinking your beer or taking a nap on your couch because the family had moved but did not tell him.