Triplex with missing lease

[Tom Bardin]

I am a first time investor and I recently have had a offer accepted on a Triplex and am going through the closing process. We have requested the lease agreements of the 3 occupied units. The seller stated that all 3 units are occupied and have year to year lease agreements. We requested the lease agreements and there was some information missing/ wrong. 1 agreement looks good and is up in October of this year. 1 agreement is from 2018-2019 and there is no paper work that says they have extended their lease. The seller has no paper work for the 3rd tenant. The seller is a older gentlemen who is having serious health issues and may not have been the best landlord. 

How do I go about acquiring a updated lease agreement for these tenants who are already in place? 

Do I request new leases be signed prior to closing? Do I wait till after we close to approach the tenants individually? 

I do not plan on doing any renovations immediately so would prefer to keep the tenants in-place.

Thanks all.