How do Long-Term Airbnb's work?

[Scott Royer]

There is a quadplex going up for sale in my area.  It looks like a great investment, and in speaking with the sellers agent, she said that the quad is fully rented with Long-Term Airbnb.  

How does this work, and is there an advantage to this strategy for a buy and hold investor?  It gives me the feeling that the current renters might not meet the qualifications I generally have for my properties.  I will have to ask more questions of the realtor, but I want to be sure that I ask the right questions.

Is there anyone out there that is currently doing this, and if so, what is your "Why?"  What are some of the questions before I possibly get myself in over my head?  Any help of information is always appreciated.  Thank you so much.