New leases when you buy a property with tenants?

[Wade Sikkink]

We just bought a 14 plex with 1 vacant unit. We made all the tenants sign a new lease with us, but one tenant is pushing back. Apparently he's a lawyer and wants to make a bunch of markup's to the lease, which I'm not crazy about.

Question is, do you really need to put new leases in place? This guy has a lease with the previous owner (no markups and strikingly similar to mine) and that lease was legally assigned to me at the closing by the seller. I'd like to know what everyone else does when they buy a property with tenants in it that they want to keep.