The house sitting assignment should end in the same spirit that it began: with an exchange of clearly expressed needs and plenty of good will. You should have the house and garden in as good a condition as when you moved in. It doesn't hurt to have the pot plants manicured, the pets bathed and brushed, the couch covers freshly laundered, the carpets vacuumed and deodorised. You get the picture.
'Be prepared for the owner's return' is your motto!It's a very good idea to have the food basics ready for them, such as fresh milk in the fridge, bread in the cupboard, a quiche in the oven and something tempting for dessert. Why not?
You may have organised with the home owner to have left before they arrive home. Your home owner may not want to enter into extensive negotiations with you about finalising the agreement upon their return. They'll probably just want to flop onto their own couch and enjoy the lovely feeling of returning to their own home. Respect their wishes whatever they are; the details of the assignment (including the return of any security deposit) can be worked out the next day or by other than face-to-face methods of communication.
Don't forget to leave your forwarding contact details!