It used to be "sleep on the floor during conferences on air mattresses, with the host providing airbeds". I personally would have had a hard time extrapolating from "surge capacity for huge numbers of people during events" to "routine spare-room or whole-house rental", which seems a lot more like homaway/vrbo/etc. to me., a good business. The former is more like couchsurfing combined with the Red Cross, and IMO not good as a business.