Any lease-option greater than 3 years is a violation of the due on sale clause by statute.

Look to bailee of personal property statutes and your responsibilities of having care, custody and control of personal property.

Every state has a statement or terms that vary including typical citations of specific state statutes that authorize LLCs.  

Usually there are statutes that directly cover the landlord-tenant relationship.

I mean, what statute or law even covers that?

Here is the statute.

The attorneys know what and what not to put in leases, know when the laws/statutes have changed, therefore keep you out of trouble.

They likely wouldn't be able to certify the closing, transfer the title, or insure the property without it (assuming that clause is the result of a local statute, which is what it sounds like), so it sounds like the seller doesn't have a choice. 

Here is the exact language from the statute: "(b) Every provision in a written instrument entered into relating to real property which purports to forbid or restrict the conveyance, encumbrance, leasing, or mortgaging of the real property for use or occupancy as a family day care home for children, is void and every restriction or prohibition in any such written instrument as to the use or occupancy of the property as a family day care home for children is void."

While we know the general facts and circumstances, and I remind all that probste laws are state specific and even those statutes can be affected by local rules of court procedurally, we don't know the case.