I looked into this as well, and got all the legal requirements for my area, and it is astounding. Where I am, if you sell soil to people, it has to be made specifically from specific ingredients that you must list and keep track of, and be responsible for not spreading soil diseases, especially if people plant them next to their existing plants. We even have to have inspections of the soil, and have lab tests done to prove it is "sterile". That's why the plants we buy at nurseries are in the weird stuff, and often suffer quite quickly if left in the pot.
It's also very risky to make representations about herbs, especially when it comes to health claims. If you go online and look at herbalist sites they rare make any claims, and discuss the plants and make some historical allusions. People can have allergic reactions, they can screw up the dosages, it's very, very tricky.
As soon as I read all of the requirements, I went straight back to growing and selling vegetables
"Life flows on within you and without you"...George Harrison
Coastal California, USA, Mediterranean climate - no summer rain, a little frost mid-winter