Is it Islamically permissible to purchase a ready-made barbershop with its workers, and to agree with these workers on a fixed monthly payment for each worker (1000 dirhams), regardless of the shop's profit or loss?

If you agree with the workers to rent them the shop for a known monthly rent, this is permissible. However, if you hire them to work and stipulate that they must collect a specific amount, and whatever exceeds it is theirs, but if they fail, they are obliged to pay it, then this is not permissible. This is because it involves consuming people's wealth unjustly, and it contains elements of ambiguity (gharar), gambling, and an invalid condition. Furthermore, a worker's wage must be known.