Someone borrowed a sum of money to set up a business. If the business proved a success and made profits, is…

Answer

The lender has no right in the profits generated by the business. Nor has he any right in demanding from the borrower any share of these profits. However, if the borrower decides, of his free will, i.e. without any prior agreement with the lender, to pay him some money over and above the amount of the debt as a favor, there is no objection to that, rather, it is mustaḥabb.