What?
Make use of homes that would otherwise be left empty while the owners are away.
Just as when living at home, home exchangers choose when laundry needs to be done (despite all those 'green' notices in hotel bathrooms to leave your towels on the floor to show when you need fresh supplies, how many times do you return to find your still clean towels replaced by freshly laundered ones?). When living in someone else's home (and they in yours) there's a great incentive to not only treat the home with care but also to avoid wasting energy and water (as most exchangers continue to pay their own household bills while away).