I hosted on Airbnb for a couple of years. My experience was that around 60% of guests are great, don't leave a huge mess, obey house rules and leave a good review. 25% are a pain, they ask for extra stuff not offered in the listing (for example, to use our washer and dryer which are explicitly NOT offered) or are very needy, constantly pestering you about how to operate the TV, asking for extra towels, etc. These guests often leave 4 star reviews, which results in drop in your host status, which is important to keep you near the top of the search rankings. The remaining 15% are in the range awful to absolutely terrible. This can range to leaving a terrible mess and smell, blood and worse on sheets and towels, blocked drains from things being put down loo or bathroom sink and my personal nadir: excrement-streaked men's underwear stuffed between the cushions on the sofa.
Forget the Airbnb deposit, getting damages from Airbnb is very difficult, and mostly they only pay you if they have been able to collect from the guest. For the damage and extra cleaning caused by the owner of the underwear, his body odour and general lack of hygiene meant I had to wash everything twice (linens, towels, duvet, mattress and pillow protectors, sofa seat covers, cushion covers) and had to take down the curtains and wash and iron those too. Airbnb compensated me £17. It cost me more than that just to clean the duvet as I had to wash it in one of those large size commercial machines. Airbnb are not interested, as they know there are lots more potential hosts, lured by the idea of easy money from renting out their spare room. If one host decides to stop hosting because of a poor experience, they will find another host (another mug!) to take their place.
But don't take my word for it. For anyone thinking of hosting, my suggestion is to log onto Airbnb, and at the foot of the listings page you will see "Community Centre". This forum contains posts and responses from lots of hosts complaining about dreadful guests, trying to get Airbnb CS to listen to them re damages, and other cautionary tales. Try searching for "guest from hell", "awful guest", filthy guest" etc. and you will see that my experience is pretty commonplace.