Tenants renting by the room

[Mickell Fowles]

I have a house that I rent by rooms individually. A tenants boyfriend has progressively started staying longer and longer and now he’s here all the time. He is not on the lease and does not pay rent. How do you handle this? My utilities are going up and with others living here parking isn’t unlimited either. What experience have you had? The room is rented to my tenant at $600 if the boyfriend stays do I have him pay an additional fee if so-with your experience about how much? 

Thank you in advance!