This information is sourced directly from the IRS Website: Here

Rental Property / Personal Use

If you rent a dwelling unit to others that you also use as a residence, limitations may apply to the rental expenses you can deduct. You're considered to use a dwelling unit as a residence if you use it for personal purposes during the tax year for more than the greater of:

  1. 14 days, or
  2. 10% of the total days you rent it to others at a fair rental price.

It's possible that you'll use more than one dwelling unit as a residence during the year. For example, if you live in your main home for 11 months, your home is a dwelling unit used as a residence. If you live in your vacation home for the other 30 days of the year, your vacation home is also a dwelling unit used as a residence unless you rent your vacation home to others at a fair rental value for 300 or more days during the year in this example.

A day of personal use of a dwelling unit is any day that it's used by:

  • You or any other person who has an interest in it, unless you rent your interest to another owner as his or her main home and the other owner pays a fair rental price under a shared equity financing agreement
  • A member of your family or of a family of any other person who has an interest in it, unless the family member uses it as his or her main home and pays a fair rental price
  • Anyone under an agreement that lets you use some other dwelling unit
  • Anyone at less than fair rental price

Minimal Rental Use

There's a special rule if you use a dwelling unit as a residence and rent it for fewer than 15 days. In this case, don't report any of the rental income and don't deduct any expenses as rental expenses.

Direct Link To IRS Article: IRS Topic 415