While I am familiar with the ADA response to this topic -essentially all favorable to a tenant, but it appears there is an abuse of the definition as they are all employed, functional individuals who leave the assistive pet at home all day.

As the lender, you should call the insurance company at closing to confirm this coverage.If he has a simple homeowners policy, like what we all have on our personal residences, he and you are likely not covered and it is possible the insurance company has what they need to deny the claim.

The first resident's request for an allergen free living situation would make it legal for the LL to deny the ESA. 

I was actually denied for the line of credit ;-(   I am working on Plan B for financing, trying to avoid using my own money as much as possible. 

We recently applied and was denied because he’s credit score is 617.

The seller can accept your request, deny it, or negotiate.

Once she applies and actually pays background and credit check, you can send a denial letter of why she was denied.

If they are being denied then the question is "what is the denial reason" and can that be overcome.

Of course they came back denying everything so we started to negotiate. 

If you insist, you will want to talk with the park owner before proceeding as they make the rules there and will have the power to approve or deny your prospective tenants.