Tattooing is a guild of professionals like any other artisan vocation, where each member is certified in some capacity as a licensed tattoo artist. This certification implies that the tattoo artist has dedicated themselves to the tattoo craft, and are in the business in order to share their art with a wider population. There is a reason why the vast majority of these licensed tattoo artists work out of a tattoo shop or parlor, as they consolidate their ownership of a proprietary entrepreneurial tattoo business in order to consistently meet the specifications necessary to maintaining professional standards and hygienic specifications of their workplace.
Home Tattoo Business
Tattooing for profit out of your home is a complex proposition, as it requires getting past a bunch of red tape and health certification codes in order to even begin your operation. In the U.S., you must first be a licensed tattoo artist to certify your adeptness at the tattooing craft, and this step in itself is a long and complicated process.
With a tattoo license, you are certified as an experienced tattooer and can easily purchase a tattoo gun and ink. Many tattoo artists start out this career path as an apprentice, working in certified shops to further gain experience with on the job training. Certified shops are a popular way for beginning tattoo artists to gain experience because they have received the health department's certification to practice body art due to their high sanitary standards. You can learn from the professional standards of these operations how tattoos are done in a safe, hygienic manner before thinking about opening your own business.
Rules and Regulations
Once you have learned the craft of tattoo art as an apprentice or otherwise, you can think about doing tattoos for free in your own home. Each state, and many countries as well, has its own rules and specifications about whether it is legal or not to do so. For example, in certain states you are required to be certified in blood-borne pathogens as a tattoo artist. So long as you are providing tattoos for individuals for free, then there are no legal repercussions because these clients are willingly being tattooed at their own risk. Keep in mind that these tattoos are riskier and generally far more unsafe than those practiced in an official studio.
The second you decide to charge from the tattoos you are providing at your home, then your business becomes decidedly illegal. It is not worth it to put your customers at risk just because you are unable to find an apprenticeship or are otherwise unwilling to share a tattoo parlor with some individuals. No state will issue a "home tattooing permit" in those terms because the home by nature is not a sanitary working environment like a tattoo parlor, and thus would never meet the health specifications necessary to establish a tattooing business.