If you're serious about your freelance business you should either become an LLC or incorporate your business. The form of business that you choose should involve a discussion between your attorney and or your CPA. We've found that business owners that treat their businesses like businesses tend to have better financial outcomes.
As a business owner you'll have a host of tax planning strategies available to you. In addition to the asset and creditor protections afforded to you by organizing as a corporation or LLC, you'll also have the opportunity to use the tax code to your advantage to possibly minimize your taxable income while contributing more to your retirement (through a SEP, SIMPLE or solo 401k, for example) and even supplementing your health insurance benefits (with the use of a Section 105 Medical Expense Reimbursement Plan).
To determine the best way to treat this type of income, you'll need to do a pro forma of the projected income, expenses and taxes. There are off-the-shelf programs that can do this. Or your financial adviser or tax preparer may be able to do this for you.