To add to @Carl 's answer, the IRS says that the costs of "keeping up a home" include such things as rent, mortgage interest, real estate taxes, insurance on the home, repairs, utilities, and food eaten in the home.
To file HOH you must have paid more than half of these costs on your parents' home - along with the other requirements.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
