Can I use a different name for my business other than my legal name?

First, there's no specific "self-employment" registry. If you plan to operate a business in the state of North Carolina, you need to register with the Secretary of State. You would need to choose a specific entity form type (LLC, Inc, etc) and you would also need to choose how your entity would be taxed (some form types don't get a "choice" per se). But as a self-employed person, many opt to create a LLC as a "disregarded entity" with the IRS. This means that you have a business entity, with an IRS-provided TaxID number, and the protections of a limited liability company. But from a TAX perspective, the IRS would "disregard" the business and simply tax you on the earnings of the business. This can be of significance, so you'll want to talk with an attorney and/or a tax professional (CPA) about your planned activities and both your entity form type and your tax type so that you can optimize your choices. If you were to be an LLC as a disregarded entity (a sole proprietor), then you would owe both the taxes on your FTE wages as well as self-employed taxes (at a tax rate determined by your total earnings) on the money from your side job. So using round numbers, pretend tax rates and ignoring the concept of withholding, let's assume that your current federal effective tax rate is 20% and that you make $100K/year. You'd owe $20K in federal tax for your income. But if your side hustle also made $100K/year, your effective tax rate could creep higher (as an incremental tax, not every dollar is taxed at the same rate) to say, 22%, so you could end up owing $44K in tax. Which might be fine with you... until you forget to pay estimated taxes throughout the year and the IRS then penalizes you for not paying them a percentage of your earnings throughout the year (whereas the withholding payments from your FTE job are typically seen as those payments). All in all, there are a TON of considerations for doing this and it's not something you should just look online for free advice to fully answer.

Never sign a contract without a lawyer reviewing it. Signing a document and being obligated to a contract that has not been reviewed can be detrimental to your business. If you and the other party disagree on the agreement, it will cost approximately 5-10 times more to litigate and defend yourself than it would cost to review the initial document and ensure you and your company are protected. DISCLAIMER The answers to these questions do not constitute legal advice and does not create an attorney-client relationship with the attorney and anyone who reviews these responses.

You can amend your filing. Please see this link https://dos.ny.gov/file-amendment.

I suggest you send the contractor an email and mail a written letter to him stating that you will not be completing the job with him.

An attorney would have to review the agreements.