Unfortunately, the down payment on a second home is not tax-deductible.

However, you may report the mortgage interest, property taxes, and private mortgage insurance (PMI) that you paid during the year. These expenses are entered under Deductions & Credits >> Your Home in the same section as the interest & taxes on your primary residence.

To find this section in TurboTax, open your return, then go to My Account >> Tools >> Topic Search. Type in "mortgage interest", then click the topic in the list and GO to go directly to the start of this section. Follow the prompts to enter your expenses for your second home.