There's nothing to 'negotiate." The landlord is demanding the contracts. If the chapter and its officers are against it they can say no to the landlord and continue to allow the non-resident members access to the property.
Then it's up to the landlord to make the next move. What that can be is impossible to predict but his options include letting it go, evicting the chapter (which likely would not hold up in court), call the police and report non-resident members as trespassers (unlikely that the police would get involved once apprised of the real situation) or just non-renew the lease when next it expires, at which time the landlord would have a lot more leverage if the chapter wanted to stay there.
The fraternity chapter is the tenant. The non-resident members are also "tenants" to the extent that they have access to the property as part of their membership. That being the case, the statutory provision I quoted earlier wouldn't apply and the landlord would just be breaching the lease by trying to essentially charge the "chapter" the additional security deposits that are not specified in the current lease.
They probably already are, IF the lease already holds the chapter responsible for the acts of the members and IF the membership in the chapter holds the members responsible for their actions.
And they would certainly be accountable for their negligent or intentional acts that cause damage to the property. ("Animal House" comes to mind.


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Then it's up to the chapter officers to refuse to go along with the owner's demands and then see what happens. Keeping in mind that, upon expiration of the current lease, the owner can impose any conditions for the new lease as long as those conditions are not prohibited by law. Since the PA security deposit statute does not apply to commercial rental agreements the landlord could jack up the security deposit for the chapter to whatever level makes him comfortable with the occupancy.
Then it's up to the chapter officers to decide to relocate or accept the new lease under the new terms.
My questions:
Will the non-resident members just refuse the contracts? You do understand that they cannot be forced to sign them.
Will the chapter officers back them up by telling the landlord to pound sand?
Will the landlord attempt to retaliate for the refusal?
Keep in mind that I haven't read the lease but I think he would not be successful in evicting through the courts base on the refusals to sign the contracts.
Beyond that, it's anybody's guess as to what might happen.
I think you and I will be continuing this discussion as developments unfold. Please continue to use this thread and not open up any new ones. It's best to have all the background in one place.