Adding a roommate/co-tenant

[Greg Pawluk]

I have been MIA for a bit between a newborn, work, going back to school.... so I appreciate any feedback.

My current rental is going smooth.  Tenant is awesome. Responsive, alert, timely.  

She requested to add her brother to lease as he needs a place to live.  He sent an application.  I would not rent to him alone, based on income/rent ratio and credit.  

How do I add him to lease, but eliminate the possibility of her leaving and him staying ever down the road.  AKA, if she goes, he goes.  Essentially he can live there with you, but everything else stays the same.

New to this managing thing. 

Thanks