Why's "subject to the vacant possession of the Premises be ready to be delivered to the Tenant" wrong?

The landlord’s realtor keeps insisting that "be" is correct. She repeats she’s been practicing real license for at least 20 years, and she’s read thousands of these clauses. She asked if I can explain the linguistics. I still think "be" is wrong, but I can’t explain. Can you? Thanks!

She’s licensed. I don’t think English is her native tongue when she speaks English with a Hispanic accent. English is my native tongue, but I never studied English after high school.

1. The tenancy’s commencement date is subject to the vacant possession of the Premises be ready
   to be delivered to the Tenant and/or the completion of the Landlord’s provision.

I think this will be correct if a gerund, "being", replaces "be". But what’s the linguistics reason?

2. The tenancy’s commencement date is subject to the vacant possession of the Premises being ready
   to be delivered to the Tenant and/or the completion of the Landlord’s provision.