A tree house. A free house. A secret you and me house. A high up in the leafy branches cozy as can be house. A street house. A neat house. A be sure and wipe your feet house, is not my kind of house at all, Lets go live in a tree house!
You can build a tree house in your back yard as an office or extra room, or guest house or if you really love your kids a play house for them. But I am not so sure you want to waste this kind of awesomeness on kids.