Is it permissible to take a 20% share of the agreed-upon profits from buying and selling real estate, prior to the actual sale of the property?

If a profit appears in a Mudarabah sale, the worker has the right to demand the sale to obtain his share of the profit, and the capitalist is compelled to sell if he refuses. If no profit appears, the capitalist is not compelled to sell. And if the capitalist offers to pay the worker his share of the profit without a sale, the worker has no right to demand the sale.