The price or the charge depends on the area where it is taking and the constraints in that place. If its taking place then one has to charge according too what the paying capacity of the crowd present. If you wish to practice mehndi in a parlour or salon then the rates will be charged according the rates of the parlour or salon which will be on the higher end, as the customers who come to the parlour can afford a higher price. But if you wish to build a clientele then starting of at small gathering and fairs is good idea. If you are already established then the charges are as per you.
A license is required only if the product is considered cosmetic like the case of beauty products. The FDA does not consider it a cosmetic, so registering for a license is not required. But if you already have a business license then the use of black henna will attract problems as it a prohibited product because the mixing of hair dyes and PPD, which are very harmful to the skin, obtain black henna. It causes sores, burns, scars, rashes and terrible skin allergies.
When applying for a business license which is required to open a business, a good way to classify henna body art is to call it temporary tattoos, body painting or even face painting. It makes it easier this way to obtain a license. The use of natural products while practicing mehndi is a good idea. As it keeps the unwanted FDA officers of your back. Thee use of natural products is hassle free and keeps your customers wanting more.