If I buy a three-family house and discover it’s only legally approved for two units, what happens to

In Massachusetts, if you purchase a property represented as a legal three family and later discover it is only legally approved as a two family, you may be unable to lawfully occupy or rent the third unit and may need permits, zoning relief, or other municipal approval to legalize it. If the property was materially misrepresented as a lawful three family, you may also have a claim against the seller or another party responsible for the representation, depending on what was represented, what they knew or reasonably should have known, and your purchase documents. This may not apply if the property's legal use was properly disclosed before closing or the third unit can be lawfully approved.