Additional info: The accepted offer that was signed by both parties (on May 8th) stipulates that the tenants would be out by 6/28. This would be to allow time for a final walk-through prior to closing on June 30th. When we went for the home inspection on May 11th I spoke with the tenants and they were the ones who told me they had a one year lease....clearly not expiring this spring or summer. I assumed that a month and a half would be plenty of time for them to find a new place and move. However, it is one week away from closing and they don't look like they're going anywhere. There is one mom and 8 or 9 children living in the property...ages 5-25, so its pretty easy to tell if they're moving just driving by the house.
I'm a little confused over the time frame. The offer stipulates that the tenants are out by 6/28, but they have a one year lease. Is the lease up by 6/28, or did the current owner just say they would be gone without specifying how/why. If so, the current owner could have some legal liability, and you should definitely check with a lawyer.