Base price: We suggest to agree on a base price per month or per week, just for the rental, just for an occupation of only two persons. That base price should be at its lowest for rentals of 3 or 4 months and over. If the rental is shorter, it is fair that the home owner asks a surcharge. But of course this depends very much how your desired period fits in the agenda of the house. The flexibility of a winter guest can be very useful for a home owner, even if its about arriving a few days earlier or later. So just talk between the two of you and see what is the best period for the both of you.
Consumables: We suggest that Electicity, Water and Gas are charged at meter price. This way the winter guest saves some money (compared to staying home) and the home owner does not have the risk of an unexpected heavy user.
Linen: The use of linen can be included in the base price, or a surcharge can be agreed. Some home owners agree with their guests that they leave the towels and sheets (except for the last used set) washed upon departure. Winter guests usually do not mind at all to wash as they will need to wash their clothes anyway. This makes things easier for the home owner. Of course the house needs to have a washing machine for this to work.
WiFi: In many houses it is available anyway all year and will be part of the base price, but there are situations in which WiFi is contracted per month. In these situations a surcharge makes sense, so that the winter guest has the option to use it or not.
Extra guests: some home owners might ask a surcharge for having guests staying at the house, since the base price was agreed assuming an occupation of two.
Cleaning: usually it is possible to contract a regular cleaning service (at a surcharge) but many winter guests opt for doing their cleaning themselves, thus saving some money and not have the hassle of the cleaners invading the house.