Is selling visas and approving a monthly payment in exchange for allowing workers to work for their own account permissible or forbidden?

Selling visas is not permissible because a visa is a guarantee, and a guarantee is a contract of donation, not one of exchange. However, if the person who obtained the visa incurred expenses, effort, or travel in acquiring it, then he is allowed to take back the amount of his expenses along with a fair wage for his work. But making this a trade and a means of livelihood is not permissible, especially since the laws of countries prohibit it. As for workers becoming attached to you due to your cooperation with them, this is a commendable act whose reward is with Allah, for "whoever eases the burden on one in difficulty, Allah will ease his burden in this world and the Hereafter." Regarding what you previously earned from the price of visas and the monthly fee, you can refer to related fatwas.