There is no such thing as a legal consultant exam. This is because the practice of law is regulated on a state by state level. What you can do is create a corporation and compose the articles of incorporation, giving your company the power to be a legal consultant. If your state allows it, you can name yourself the president, CEO, secretary, and registered agent. I did that for my company Passaro Reid Financial Services Group, here in Florida.
Then, market yourself to attorneys only or to federal agency clients.
You have to be very, very good at what you do. "The world" will be evaluating your every move. Or, take the CLA exam and be a paralegal. The best exams available are either the latter or any state bar exam.