Yes, you can deduct your mortgage interest and real estate taxes as usual (or mortgage insurance and points if you paid any on the purchase) since the son just moved in and you didn't charge him any rent (If i'm understanding your correctly..). At this point, it is your home; you still own it. You can deduct above deductions for your primary and 2nd home in the Deductions & Credits section, Your Home category.
In 2017, if you rent it to him at FMV, the house will become your rental property, you would report rental income and your above expenses as rental expenses. When you sell it to him, it will be reported as rental property sale on your tax return.
