Starting a solo practice too early. Unless you have a fat savings account, a partner who will support you, or are willing to work some side jobs for extra cash you may not want to open an independent practice early in your career. Besides the cost of operating a solo business you are likely to lack the customers and experience of working in a well-established salon or spa. Time working for someone else at least in the first year or so will prove extremely valuable for when you are truly ready to survive on your own. Take your time, learn, make mistakes where they'll be less damaging to you, and build some customers up before setting up shop. You'll be thankful you did.