you'll find a lot of issues living in a house without a 'certificato di abitabilità', connecting utilities might be outright impossible and you might be fined/removed from the premises.
No, you cannot live in the house until it is certified as habitable. Like many things in Italy this would no doubt be flexible with the right "permits" paid for to the right officials. But the houses would likely have no working electricity, heat, water or plumbing. So you wouldn't really want to live there anyway.