One idea I recently came across is allowing people to remotely access an unused physical Android phone. The owner keeps the device at home and connected to the internet, while someone who needs a real Android device can access it remotely. I was actually researching how much can you make with a phone farm here because I have an old Samsung in a similar situation. I'm not sure the income figures people mention online would apply to every phone, though. I'd look at the model, expected availability, internet requirements, electricity usage and how much maintenance is involved before deciding whether it's worthwhile.