2. Notarization is only a way of evidence preservation (fixed evidence), and no third party can know it.
3. The house only has a contract, and there is no property right registration? Can property rights be registered (preferably not a small property right house)? If you can register, remember to add your name (* * * owner).
4. If the property is only registered (registered, not a sales contract) in your friend's name, when he resells it to a third party, the third party may acquire it in good faith (the property registration has credibility); At this point, your loss can only be recovered from your friends.