The notarised agreement cannot enforced in court of law, even if you file a suit for specific performance of contract, the court may consider this agreement as a receipt for the amount paid towards the part of sale consideration and may pass an order to return the same.
If the vendor is insisting to stay in the property temporarily after executing the registered sale deed in your favor, you may demand monthly rental amount from im and can also enter into a rental agreement with him or do not entertain his claim for staying back in the property after the property has been sold to you.
However if the vendor is still insisting on this you may ask him to give it in writing so that it would become a base for you to cancel the sale agreement and demand the return of the advance amount @ 12 % interest by communicating your decision in writing sent by registered post with acknowledgment card.
This would make the seller to re-think about his decision and may even drop his idea of staying back in the property after completion of the sale formalities.
If you are still in doubt or not able to tackle the situation properly as well as legally you can take the assistance of an advocate in the local and proceed as suggested