Inherited Tenant Expired Lease - complete a new application?

[Alicia Gates]

I'm in the due diligence phase for purchasing a SFH, and I have 2 weeks in which to decide if I'm keeping the current tenants in place through the close, or have the sellers give them a 30 day notice and deliver the property vacant at close.

I have the copy of the lease and it expired nearly a year ago, so they have defaulted to month-to-month.  I will meet them briefly tomorrow at the inspection. 

Do I have them complete a new rental application so I can do background checks, verify income, call references, etc.?  Or can I not do that since they are already tenants? I would have them complete an estoppel cert. if I decide to keep them on, but I would want to be able to verify the other information too b/c who knows what the seller's screening process was.