What is the ruling on taking a percentage of the profits or a specific amount in exchange for someone operating my trucks?

There is no impediment to taking a fixed, known fee for searching for work for a truck, provided that this does not lead to infringing upon the rights of others, that the truck is fit for work, and that the arrangement is not secured through an illicit bribe. However, taking a percentage of the truck's income is impermissible due to the excessive uncertainty (Jahalah Fahishah) associated with the contract.