They had a device they hooked up and could listen to the sound waves. 

In the infancy of this new wave of Airbnb, say 5 years ago, there was a lot of money to be had, which draws in a lot of investors, which starts to suppress the revenues and also draws attention from critics, which leads to taxation and regulation.

I have found it comes in waves or droughts. 

It really depends on their availability which seems to come in waves.  

Yes, the contractors were bad people, but there were hundreds of red flags waving in your face and you ignored them all. 

With Phoenix, I’ve got my finger on the pulse of neighborhoods where you can still snag undervalued properties and ride the wave as the city keeps booming.

Do not fall for the "its easy" responses from people and you can wave a magic wand and go out and invest in real estate (you can but will you make money).

Specific topics come in waves.

I haven't managed to get into the waves yet but they look amazing and the countryside is beautiful! 

Sometimes we have a wave of rejections in a row for a given property.