@FartingAgainstThunder This is the first time that Justice has appeared, but it doesn't surprise me that it has taken this long. She is a heavyweight card, and she only seems to appear when there are serious decisions to be made.
Like the statue of Lady Justice at The Old Bailey, she holds a sword in one hand, and scales in the other. In some Tarot she is also blindfolded, the better to be able to make an impartial decision. Like Maat, the Egyptian Goddess who weighed human hearts against a feather to see that they were free from sin, and worthy of a place in the afterlife, Justice weighs the evidence in her scales. Her sword is there as a symbol of her authority, and lets us know that her decision is final.
You ask about starting your own business. This card cannot tell you yes or no, it stands instead as a warning to not take any decision lightly. You may need to take legal advice before you decide which path to go down. Justice is there for mediation and discussion -have you talked to other people about your ideas, or asked for professional opinions? If it is still a pipe dream at the moment, she is telling you that this would be a good place to start.
In terms of what area you may be thinking of for a business, she rules all manner of admin, legal work, accountancy, mediation, counselling... anything where logic and patience is an advantage.