One of the biggest individual tax breaks is the ability of homeowners to deduct the interest they pay on their mortgages. It's claimed most frequently on the loan used to buy a taxpayer's main residence. But the mortgage interest deduction also can be claimed for second homes.
And those multiple residences don't even have to be permanent structures; a boat or RV could count. Supporters of this tax break say it's integral to making homeownership possible and keeping the housing industry afloat.
But it also comes with a high cost to the Treasury. The Joint Committee on Taxation estimates $405 billion in lost taxes on the tax break for primary residences alone.