Paperwork For Buying Commercial Shop In A Commercial Complex - UP (Ghaziabad)

The allotment letter for commercial shop I have seen from the builder to the owner is on 100 Rs. stamp paper and builder have file maintained which have payment details out of which around 10% payment is pending. Possession was done in 2018 but the registry has not been done. Now the owner is getting it registered first at his name and then next step I will register on my name. Advance (Bayana) I have given is 10 thousand but we agreed on 50,000 once the owner is present as owner stays out of town. Now the broker is actually asking for 3 lakh(15lakh is total deal) amount so that owner can register on his name. He tried to make me understand that owner does not have that much money with him to clear the Electricity/Maintenance dues + Registry+ Stamp duty. Broker said he don't want anything in cash and would create an agreement on 100 rs stamp paper. is it safe to pay the above agreement should be of any specific format? like agreement to sale or sale deed.