You're REALTOR should have been able to negotiate an arrangement with the seller. Usually I would say he is in breach of his contract, but you say you don't have a contract with him, so I'm guessing you bought directly from the current owner.
He is technically now your tenant. Our purchase contracts protect the buyer by making arrangements for the seller to pay rent to the buyer if he does not vacate by the agreed upon date. Without a contract, spelling out his duties, you may be left to the local authorities. Also, if he is "tearing up the house" the damage would fall under your insurance.