Freelancers pay both halves of FICA — 15.3% self-employment tax — plus regular income tax on net earnings.
15.3%: 12.4% Social Security (up to the wage base) + 2.9% Medicare, applied to 92.35% of net earnings.
Yes — half of your self-employment tax is deductible from income tax as an above-the-line deduction.
Generally yes — estimated taxes are due four times a year if you expect to owe $1,000 or more.