Buying a property with tenants, Month to month without contract

[Matt Laird]

I'm a few weeks away from the closing table, deal looks good, 3 units on one property, 2 units are leased $450 month(which is below market value) current owners didn't do background checks or sign leases. They have been on a month to month basis, one near 3 yrs. and one just over 1 year. One tenant has an aggressive bred puppy, looks like a pit/boxer cross, & I do not allow pets in my other rentals.

My question to the experts is; can I force the seller to do a background check and get a lease signed before closing or have them vacate, should I go talk to the tenants myself. I'm afraid once I sign on the property I may be locked in a deal with squatters and spend my first few months in the hole working on evictions..

Thanks in advance Matt...