Hi,

Your lender may be right, but it depends entirely on how your property is classified - and that classification matters a lot.  Let me give you the citation you need and explain the distinction.

The key question: duplex or ADU?

If your property is a true 2-unit property - a legal duplex with two separate dwelling units - HUD does not specify which unit you must occupy.  You can live in either one.  The requirement is simply that you occupy one of the units as your principal residence.

If your property is classified as a single-family home with an Accessory Dwelling Unit (ADU), the rules are different.  In that case, HUD requires the borrower to occupy the primary unit, not the ADU.  The ADU is considered subordinate to the main dwelling.

The citation you can give your lender.

The relevant authority is HUD Handbook 4000.1, Section II.B.2.iii(B)(4) - Accessory Dwelling Units, and Section II.B.2.iii(B)(2) - 2-Unit Properties. You can access the current version of the handbook directly here:

HUD Handbook 4000.1 - Full PDF

The ADU definition and occupancy requirements are on pages 585-586 of the PDF. The 2-unit property requirements are on page 585 of the PDF.

For the ADU section specifically, 4000.1 defines an ADU as "a single habitable living unit with means of separate ingress and egress that meets the minimum requirements for a living unit" that is "subordinate in size and within, or detached from a primary one-unit Single Family dwelling." A one-unit property with a single ADU remains classified as a one-unit property.

How the classification gets determined

The appraiser makes the initial determination based on the property's physical characteristics, local zoning, and highest and best use analysis.  The key factors are relative size, whether the second unit has always been used as a separate independent dwelling, and how the local jurisdiction classifies it.

If the smaller unit you live in is clearly subordinate in size to the larger unit, and the property is located in single-family zoning, the appraiser will likely classify it as a single-family home with an ADU.  In that case, your lender is correct, and you would need to occupy the larger unit.

If the property is legally zoned and recorded as a 2-unit property with two separate, comparable dwelling units, the duplex rules apply, and you can occupy either unit.

How to challenge the classification

If you believe your property is a true duplex and not a single-family home with an ADU, here is what you need to show your lender.

First, pull the property's legal description and zoning classification from your local assessor or planning department.  If it is legally recorded as a 2-unit property, that is your strongest argument.

Second, ask the appraiser to document the highest and best use analysis and confirm whether the property meets the definition of a 2-unit property based on comparable 2-unit sales in the area.

Third, if the lender still disagrees, you have the right to request a second appraiser through the lender.  You cannot select the appraiser yourself, but you can ask the lender to assign a different one if you believe the first appraiser's classification was incorrect.

The distinction between a legal duplex and a single-family home with an ADU is a factual determination based on the property - not something the lender gets to decide arbitrarily.  The handbook citation above provides the policy foundation for that conversation.

Reference: HUD Handbook 4000.1, Section II.B.2.iii(B)(4) - Accessory Dwelling Units and Section II.B.2.iii(B)(2) - 2-Unit Properties (PDF pages 585-586).