The situation, a loan on a mobile home park; the person who rents the lot and owns the manufactured home (not used as collateral) puts an outbuilding/shed on the lot. If the land is in a positive flood zone, would flood insurance be required on the outbuilding/shed?

I am not sure I understand. Your collateral is the mobile home park. One of the renters puts a shed on their lot? I doubt your security interest would reach that shed as it will remain the property of the renter. That would be considered a leasehold improvement and you would have no more of a security interest in it than you would any mobile home that a renter placed on their lot.