what are some things you wish you knew before you started doing Air Bnb? 

Last think you need is for a furnace or a water heater to go and have to scramble to come up with the funds out of thin air. 

Some want to Air BnB.

Previous to renting it was just me and my wife and we did not use the air conditioning much.

I've called AIR and they have promised to have their tech support look into it, but all they do is send me a link on how to sync calendars....!

This is a form of rental arbitrage and is talked about here from time to time but it is usually where the renter is putting it on air b&b where the spread will be larger than with long term but there is also more work involved.  

I found that I liked air flow through the house and accomplished it with just the fan of the furnace but I didn't have to use the AC.

I wonder if this could affect vacation rentals, i.e. a guest arrives with a dog, and even though we clearly state on AIR and VRBO that pets are not allowed, here they are anyway.

Air conditioner is over 10 and for expense planning purposes we can expect to replace that within 5 years. 

My first deal was a condo and I used air bnb to short term rent it, to later realize 30 days and under renting is not allowed.