It's illegal to mislead your lender about whether your second property will be used to earn income. A common lie that homeowners make to mortgage lenders is to classify their purchase as a second home, when they actually intend to use it primarily for rental income. Intentionally misrepresenting the intended use of a property to obtain more lenient mortgage terms is called occupancy fraud and can lead to hefty fines.
Occupancy fraud may also put you in default of your loan agreement, which can mean forfeiting your home. Many high-tech lenders also now have access to digital verification processes that identify the most likely instances of fraud. Some mortgage companies will go so far as to schedule random site visits to verify who actually resides in the property.