Is an agreement to give 5% of the project value to a friend, in exchange for using his company's name and documents, permissible in Islamic law? And is this agreement better, or is it better to lease the company's name monthly?

Scholars have differed on the ruling of taking money for sponsorship (price of influence), with various opinions. We have favored its permissibility to the extent of the prevailing wage for such services (ujrat al-mithl). It is not permissible for it to be a percentage of the value of projects or their profits due to ignorance (jahalah) [uncertainty], and the safest approach is for it to be a fixed amount, whether monthly or annually, or according to agreement. Alternatively, the owner of the institution could enter as a partner with his wealth, and thus receive a share of the profit.