Is it permissible to sell a plot of land to a person who will then sell it for another price, in exchange for giving him its original price?

If the intention is to set a price for the land to sell it at a higher price and allocate the increase to the seller or divide it between them, then there is no objection to that. This is called brokerage (simsarah), and many scholars have permitted it. Al-Bukhari said: "Chapter on the Broker's Fee." Ibn Sirin, Ata, Ibrahim, and Al-Hasan saw no harm in the broker's fee. Ibn Abbas said: "There is no harm in saying: 'Sell this garment, and whatever exceeds such and such [a price] is yours.'" The Prophet (peace be upon him) said: "Muslims are bound by their conditions." Therefore, the seller can give his land to the broker and set a price, and whatever exceeds that will be for the broker or divided between them by a certain percentage.