Regarding sale of property

I have a property in another city in India. The buyer of the property has currently paid me a small token amount only. All discussions with the buyer are currently only verbal and no written evidence. As it is not an auspicious month for purchase of property, starting next week, the buyer wants that i hand over the house key to the buyer to carry on the paint jobs and other repair works so that the house is ready for move in by the time the auspicious month begins and they can move in by Diwali in end Oct. Is it fine to do so or should I tell them clearly that house key can only be handed over after we have completed the sale deed. Please advice. Also, is it legally correct to give keys to a buyer without a sale deed? If buyer insists for key can we make an agreement to sale and ask buyer to pay a certain proportion of sale price and then hand over the key to them to commence work, so that by end of Oct both the repair work is complete and the sale deed process is also done. If needed we can include a clause for this in the agreement to sale. Is this allowed in eyes of law?