I bought a house that was empty after divorce, both had moved out some months before. We mostly dealt with the agent, only saw one of the previous owners for a very short time at the signing meeting with the notary.
Then in the house we found a "congratulations on your new place" card, a bottle of sparkling wine, and a binder with everything about the house. Building plans, updated plans for changes made, exactly where every cable and connection was, and manuals, invoices and warranty certificates for equipment in the house. And a hand drawn map of the garden with what type of plant was where, and links to plant care instructions for some of the more exotic plants.
Super nice of the previous owner to arrange these things, and I'm still thankful every time I need to get a cable somewhere or do some small construction things. Having detailed and accurate plans and overviews saves a lot of time.