How to verify the actual purchase price of property?

Could you please advice, how to authenticate the actual purchase price of property? What is the legal document involved in this process?

Regards,

Due to dealers game, it's very difficult now days to find actual price, until you meet with the seller personally and agreed on some deal price.

dealers network is strong and it's mafia now days.

Agree with Siddique. Even direct dealing is hard these days. I sold a plot two years ago and after the transfer and payment of commission to dealer, I found out that buyer was brother of this dealer.