Just to clarify things a bit:
1. A 1099 is a form that is issued to you at year's end by anyone who has paid you $600 or more that year for services you've provided to them in the course of their trade or business. These forms are sent to you at year's end. It is not a form that you issue unless you have paid someone else more than $600 in a year for their services. It is your client's obligation to send the 1099 to you. But you must keep track of all your income because you must report it all, whether you've received a 1099 or not.
2. The income you earn as a free-lancer is considered self-employed income, and is reported by you on Schedule C, which is part of your federal tax return. You must file a tax return in your own name if your total net self-employed income for the year is $400 or more. Your net income is your gross income for the year minus any expenses you have related to your free-lance services. It follows that you should keep a record of any expenses you incur related to your work.
3. If you were an employee (as opposed to a free-lance worker), your employer would issue you a W-2 at year's end, reporting your income for the year. The W-2 would show the federal taxes your employer has withheld and paid for you during the year. As a free-lancer (also known as an independent contractor) you do not receive a W-2, and your clients do not withhold taxes for you. Since the IRS is a pay-as-you-go operation, a free-lancer is expected to make quarterly payments to the IRS of his "estimated" taxes. This IRS reference explains more about that:
https://www.irs.gov/businesses/small-businesses-self-employed/self-employed-individuals-tax-center
4. The only annual form you have to fill out is your tax return itself.
None of this is as complicated as it sounds. You're probably a smart kid, and I think you'll get the hang of it all pretty quickly. Good luck.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
