It is pretty wild how much the rental industry has grown over the last ten years. Airbnb completely flipped the market upside down. Before Airbnb a normal home owner might not have been inclined to try to rent out any free bedrooms in their home. Now people are using it as another source of income, kinda like Uber.
I have actually been able to stay for free the last few times I went on vacation. I did this by switching homes with another person in the area I was planning on vacationing. At the same time I was using someones home in upstate New York, I would be renting out my house in California....or even better make a straight up trade with the other homeowner.
That way my house is making me money while on vacation :)