Wednesday Whatsapp Challenge

You borrow money from a friend to help start a business. Six months after you repay the loan your friend asks to rent your cottage. You tell them you are happy to do so. Can you offer the place for free as a sign of gratitude ? Must you charge so it is not "interest"? Can you tell them thank you for the loan so please enjoy the cottage and do not pay me? What about if it is an issue and you realize it only after a few days? Do you have to pay for the fair market value of the week? Or maybe, the loan from 6 months ago has nothing to do with each other so you can say or do whatever you want?!? Please explain