Accepting Payment and Lease Renewal for Existing Tenants

[John Lyszczyk]

Hello BP Community, 

My brother and I are moving into a duplex with an existing tenant on the bottom half of the house.  We are honoring their current lease, but I want to make sure I receive payment from them AND have a leg to stand on if they decide not to pay rent.  

What documents should I have them sign? Their current lease agreement expires at the end of the year and I will have them sign our lease agreement when that time comes.  

My question is: what do I do in the meantime to make sure that I am their legal landlord and they are contractually obligated to pay me?