There is no simple answer to this question.
If this is your primary residence, and you were out of town and your friend did you a favor and performed house sitting duties for a relatively small amount of time, then you simply file as normal.
This may not apply, if this was for a "lengthy period of time," as such it could be considered rental property and business rules and regulations would apply.
If the house was up for sale during this period of time, and he was occupying the house to prevent criminal activity or squatters, different accounting rules apply.
If you normally rent the house out, but did not charge rent to a friend, then, depending upon the current laws, you may need to provide your friend a record of reportable income, as he is getting free rent from you. The rest of the expenses associated for the house is then considered a rental expense based upon current rules and regulations.
However, if the friend is "house sitting" for you in the event you cannot rent the house, then you should be able to expense the rent during that time, while providing the friend an equal amount of reportable income.
One thing to consider is that your insurance/rental/business efforts need to be in synch.
In your situation, I would obtain the advice of a tax accountant, and file for an extension. TurboTax will prepare your taxes based upon your entries. Correct entries may require the advice of a tax accountant.
