According to this source, I would not need a license to be a freelance editor. But if I had a business, the source says I may need to register the business, and I also may need a vendor's license depending on the circumstances.
However, would I need to undergo any registration if I edit a single author's books? Also, would my services be taxable? If relevant, assume I am paid per page.
Editing is protected speech under the First Amendment. The government may not require any license to perform such services, though an author could impose whatever credentialing requirements she chooses.
If you have created a business to provide those services, that business may need to be registered with/licensed to business in the state generally, but again, it would not require any special licesnse to perform editing services.
Whether you provide those services as an individual or as the agent of a business entity, any income you derive from editing is subject to taxation the same as any other income you receive.
I'm inclined to agree with the taxforwriters.com source linked to by the original poster, The Editor.
Usually states don't tax services such as accounting, engineering, lawn mowing, etc. under the sales tax laws. This makes it different from things like garbage bags and backpacks. There are some exceptions.
States may or may not require licensing or registration of businesses. This may be required at the state or local level. The purpose sometimes is to levy yet another tax, and sometimes it is just to keep track of who is doing business in their jurisdiction. Usually there is no need to prove any competency in the chosen field of business. In addition to sales taxes, if any, the net income may be subject to corporate or personal income tax.
States also license certain professions, such as lawyers, engineers, medical doctors, etc. To be granted such a license the professional must prove competency by showing university degrees, letters of reference, etc., and may have to pass a national or state exam. The professional license may also serve as a business license.
Some professions do not need this kind of license, either because malpractice wouldn't pose much of a threat to the public, or attempting to regulate them would be too much of an infringement on liberty. For these reasons, I'd be surprised if any state tried to make writers or religious leaders become licensed professionals (and I'd lump editors in with writers).
