Tenants Who Air BnB Apartment Units

[Gerrit Bruni]

Hello! I recently purchased a 6 unit apartment building and have tenants who do Air BnB in half the units. My question for everyone here, how do you base rent for tenants who utilize the unit for their Air BnB? I'm new to this concept and want to charge a fair price for this but also cover my risk. 

Side question: do you allow tenants to do this on your property?

Thank you so much for your input!
-Gerrit