An ESA letter for Housing is an official document written and signed by a state-licensed health professional on official letterhead. This document is proof that the pet is part of the treatment plan for the person claiming reasonable accommodation for their emotional or mental sickness. It is also known as reasonable supporting documentation that specifically offers the following benefits to the ESA owners;

It allows owners to Stay with ESA in a no-pet apartment, building, house, etc.
It exempts them from paying extra pet or security fees to the landlord.
It offers the owners with the liberty to stay with any animal irrespective of its breed, size, or weight. A Housing ESA letter restricts the landlord from rejecting the request for making reasonable accommodation based on the parameters of assistance animal.