Tenants at Will, Smoking, Cleanup

[Kimber Lockhart]

I'm closing on a property with existing tenants (in Oakland, rent controlled).  There are no known leases for a couple of units.  

I'd like to ban indoor smoking, remove some no-op vehicles and organize storage.  I have heard it might be possible to enact a smoking ban that isn't on the lease and remove safety hazards.  Anybody been here and have advice?