It's complicated..... they will do it .... sometimes.
The property has to have comparable properties that are similar to allow the appraiser to do valid comps (so other homes in the area with large acre lots and single wide accessory units).
I've also seen it done where the utilities are turned off and the appraiser comments that it has no value/is just storage(outbuilding).
Fannie Mae has the following guidelines:
For ADU's:
https://selling-guide.fanniemae.com/Selling-Guide/Origination-thru-Closing/Subpart-B2-Eligibility/Chapter-B2-3-Property-Eligibility/1032991541/B2-3-04-Special-Property-Eligibility-Considerations-09-02-2020.htm?touchpoint=Guide&fbclid=IwAR3CvOWiQcQ5-NO_qtq475J5rXmvBdeE4yvQYokpBltH3IRkcxRljAY_Nj8#Accessory.20Dwelling.20UnitsConstruction of an ADU
The construction method of an ADU can be site- or factory-built, including modular, and single- or multi-width HUD Code manufactured homes that are legally classified as real property. If an ADU is present, the primary dwelling must be site-built or a modular home. If the ADU is a HUD Code manufactured home, the lender must verify the following:
the property was built in compliance with the Federal Manufactured Home Construction and Safety Standards (established June 15, 1976, as amended and in force at the time the home was manufactured),
it is attached to a permanent foundation system in accordance with the manufacturer’s requirements for anchoring, support, stability, and maintenance,
the foundation system must be appropriate for the soil conditions for the site and meet local and state codes,
it is encumbered by the mortgage with the primary dwelling, and
additional requirements that appear in HUD regulations in 24 C.F.R. Part 3280.
Compliance with these standards will be evidenced by photos of the HUD Data Plate and HUD Certification Label(s) in the appraisal. If the original or alternative documentation cannot be obtained for the Data Plate or HUD Certification Label(s), the loan is not eligible for delivery to Fannie Mae. See B2-3-02, Special Property Eligibility and Underwriting Considerations: Factory-Built Housing, for more information.
For Outbuildings:
https://selling-guide.fanniemae.com/Selling-Guide/Origination-thru-Closing/Subpart-B4-Underwriting-Property/Chapter-B4-1-Appraisal-Requirements/Section-B4-1-3-Appraisal-Report-Assessment/1032992541/B4-1-3-05-Improvements-Section-of-the-Appraisal-Report-09-02-2020.htm#Properties.20with.20OutbuildingsProperties with Outbuildings
A lender must give properties with outbuildings special consideration in the appraisal report review to ensure that the property is residential in nature. Descriptions of the outbuildings should be reported in the Improvements and Sales Comparison Approach sections of the appraisal report form.
Type of Outbuilding
Minimal outbuildings, such as small barns or stables, that are of relatively insignificant value in relation to the total appraised value of the subject property. The appraiser must demonstrate through the use of comparable sales with similar amenities that the improvements are typical of other residential properties in the subject area for which an active, viable residential market exists.
An atypical minimal outbuilding-The property is acceptable provided the appraiser’s analysis reflects little or no contributory value for it.
Significant outbuildings, such as silos, large barns, storage areas, or facilities for farm-type animals. The presence of the outbuildings may indicate that the property is agricultural in nature. The lender must determine whether the property is residential in nature, regardless of whether the appraiser assigns value to the outbuildings.
Freddie Mac has the following guidelines:
https://guide.freddiemac.com/app/guide/section/5601.12 Outbuildings on a property:
Outbuildings on a property, such as barns or stables, must be considered in the underwriting process to determine whether the property is primarily residential or non-residential. A property with a small barn or stable may be acceptable if the contributory value of the outbuilding(s) is minimal in relation to the total appraised value of the subject property. The appraiser must demonstrate in the appraisal (e.g., through the use of comparable sales, pending sales or listings) that these characteristics are typical for residential properties in the market area.
ADUs:
Manufactured Home accessory unit
Freddie Mac will purchase a Mortgage on a one-unit dwelling that contains a Manufactured Home accessory unit that meets the requirements for a property with an accessory unit and the following:
The Manufactured Home meets the property eligibility requirements of Section 5703.2 and titling and lien requirements of Section 5703.7
The Manufactured Home accessory unit must be legally classified as real property
A Manufactured Home accessory unit must have a minimum of 400 square feet of gross living area and meet the HUD Codes for Manufactured Homes (HUD Codes)
A Manufactured Home may not be an accessory unit for a Mortgage secured by a Manufactured Home. However, this does not apply when the Mortgage is secured by a CHOICEHome®.
The appraisal report for a 1-unit property with a Manufactured Home accessory unit must include the following:
Confirmation that the HUD Data Plate/Compliance Certificate is attached to the dwelling. If not attached, the appraiser must provide the data source(s) for the HUD Data Plate/Compliance Certificate information reported.
Confirmation that the Wind, Roof Load and Thermal Zones meet the minimum HUD requirements for the location of the subject property. If the unit does not meet these requirements, the appraiser must address.
Confirmation that the HUD Certification Label is attached to the exterior of each section of the dwelling. If not attached, the appraiser must provide the data source(s) for the HUD Certification Label information reported.
Manufacturer's Serial #(s)/VIN #(s)
HUD Certification Label #(s)
Manufacturer's Name
Trade/Model
Date of Manufacture
Describe any additions or modifications made to the Manufactured Home (decks, rooms, remodeling, etc.). See Section 5703.2 for property eligibility for Manufactured Homes.
