Is it permissible to take the price of a plot of land from a friend and return to him a plot of land of the same area and location later?

If you take the payment, it becomes a debt upon you, and the rulings of a loan apply to it. A loan is to be repaid with its equivalent, and stipulating an increase is impermissible; otherwise, it would be usury (riba). However, if the debtor repays his debt and wishes to add something to it as a gesture of kindness and recompense for the favor, without any condition from the creditor, then this is praiseworthy (mustahabb). Accordingly, if you wish to repay your friend, it is permissible for you to offer him repayment with a piece of land. If he agrees, then there is no harm.