24 C.F.R. § 100.203

(a) It shall be unlawful for any person to refuse to permit, at the expense of a handicapped person, reasonable modifications of existing premises, occupied or to be occupied by a handicapped person, if the proposed modifications may be necessary to afford the handicapped person full enjoyment of the premises of a dwelling. In the case of a rental, the landlord may, where it is reasonable to do so, condition permission for a modification on the renter agreeing to restore the interior of the premises to the condition that existed before the modification, reasonable wear and tear excepted. The landlord may not increase for handicapped persons any customarily required security deposit. However, where it is necessary in order to ensure with reasonable certainty that funds will be available to pay for the restorations at the end of the tenancy, the landlord may negotiate as part of such a restoration agreement a provision requiring that the tenant pay into an interest bearing escrow account, over a reasonable period, a reasonable amount of money not to exceed the cost of the restorations. The interest in any such account shall accrue to the benefit of the tenant.

(b) A landlord may condition permission for a modification on the renter providing a reasonable description of the proposed modifications as well as reasonable assurances that the work will be done in a workmanlike manner and that any required building permits will be obtained.

(c) The application of paragraph (a) of this section may be illustrated by the following examples: