I only own one house, and I live it in full time (all year).  I set-up a room to begin renting in November (didn't get a tenant until December).  When entering information for renting out the room, it describes how it's still rental property, just a "portion of a single property."  

I entered my 1098 information on the Deductions and Credits (entering my Mortgage interest, real estate taxes, mortgage insurance premiums, etc.); THEN, it also requested this SAME information for the rental property.  After I entered it for the rental property, my estimated federal refund skyrocketed (doubled!).  I feel like I may have entered this incorrectly because I didn't expect this to happen, especially since I only received income for the room for  less than one month (28 days) and a security deposit (roommate still living with me).