If your son files as Self-Employed and reports his 1099-Misc as Business Income, he may owe Self-Employment Tax even if he has other Federal Deductions.
He can review his return in TurboTax Online by going to Tax Tools > Tools in the left-side menu, then choose 'View Tax Summary' from the pop-up menu. Then, back at the left-side menu, choose 'Preview My 1040'.