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There is a maximum and you do not have to pay the 6.2% for FICA; but there is no maximum for Medicare so you do have to pay 2.9% (both the employer and employee rates of 1.45% each) in addition to income tax.
See Social Security and Medicare Taxes for the yearly maximum amount.
If you have any expenses related to earning the income from freelancing you will be able to deduct those expenses and only pay income tax and Medicare on the net income by filing Schedule C
I hope this helps for estimating the tax due on the income reported on the 1099.