I have read out your query and propose you the following legal advise:
Firstly, Check the validity of the property mortgaged, there have been various instances that the property is being mortgaged to 2 or more banks and there is a pending litigation in DRT (Debt Recovery Tribunal). So please make sure that the property is free from all encumbrances and there is no pending litigation upon the said property.
Secondly, If he is asking you to transfer 10 lakhs in advance to his account, you can always do that if you mutually agree and there is a sense of security that he would not run away with the money as the title deeds are not with you and not in your name so you have to be cautious while performing this transaction. It would be better if you issue him a cheque for the like amount.
Thirdly, an unregistered sale deed has no value in the eyes of law, if any dispute dispute arises on the property then your sale agreement would not serve as an evidence in court of law. Sale agreement is different from Sale deed. so it is preferable that a registered sale deed should be executed. An unregistered sale agreement would be for your own satisfaction, but if in future anyone claims that he has the registered sale deed, then your agreement to sale would have no evidentiary value in a court of law.
I hope i have provided you relevant information. Please leave a rating if your are satisfied with your answer and I would get back to you again.
Thanks and Regards!
Varun Talwar, Advocate Delhi High Court.