rental income

My family did Airbnb last month. We rented a nice cottage in northern Michigan. The price was right and it was comfortable…except for the ants. There weren’t a lot, but enough that I emailed the home owner/ host. She never responded but we dealt with it. After all, our expectations weren’t as high as if it were a hotel. Our host was sharing her home and we had a friendly, casual relationship. Or did we? When does sharing for a fee morph into something more formal?