My wife and I often take care of other peoples' dogs. One of the ones we don't actually take care of but who see a lot of is our neighbor's Great Dane (we cut a hole in the fence so he can come over anytime he wants).
Our neighbors treat him well, but he likes to hang out at our place. He waits for us every day when we come home, and he stays with us for dinner and hangs around in the house until we send him home at 10pm.
A few minutes ago, our neighbor popped by -- wanted to take his own doggie for a walk I hope he comes over afterwards. We're very used to him and the house seems desolate when he's not around.
BTW, I have talked to our neighbors several times about this because I wouldn't be happy if someone else just put my dog in their house. However, they're totally cool with it. They even appreciate that we run him out of energy so he doesn't tear their house apart.