We have a separate apartment in our house, and we rented it for a year to a friend, which turned out to be a bad move--he left it inconceivably filthy, stopped paying his rent 10 months in and strung us along, damaged stuff through sheer carelessness... it was NOT good for our friendship and while the money was obviously welcome (he was paying about 1/4 of our mortgage), it was SO unpleasant.
So after he moved out we left it empty for many months, enjoying the peace and quiet and the ability to put our visiting relatives up in the apartment when they came, but obviously missing the money. And then last month a friend of mine mentioned that she and her husband rent out their spare rooms on Air Bnb. I can't believe that hadn't occurred to me before, but it hadn't.
So we hauled some spare furniture up there, took photos, I spent a few hours putting together a really great looking and sounding Air Bnb listing and... in the first month we've had visitors every weekend, some short weekends and some long--in other words people have been here for about 10 of the 31 days of the month--and in those 10 days we've made just $56 less than we did by renting the place for a solid month to our slobby friend! I certainly hope this keeps up! Even if it doesn't bring in quite as much money, it still brings in a lot and the trade-off of only having people here on weekends and knowing that if we get bad guests we're not stuck in a lease with them... is FANTASTIC. And of course we can just decide to make the place unavailable whenever we want to put visiting friends or family in it.
I also put an ad up in the short-term rentals section of Craigslist and had two people email about it within less than two days of putting the ad up. I referred them to our Air Bnb ad so they could book the place for the month or two months that they wanted (our per-month price on Air Bnb is almost double what our friend was paying us).
In short... so far this RULES. Has anybody else had experiences hosting on Air Bnb, good or bad?