Varies state to state, although the (U.S.) convention is to require a 65 of everyone. Check your Sec.y of State.
There are some state exemptions for a small number of accounts. You have to check with your state. Where will your place of business be?
http://www.flofr.com/StaticPages/DivisionOfSecuritiesFAQ.htm 2. What is Florida's de minimis exemption for Federal Covered and State Registered Investment Advisers? Florida's de minimis exemption for investment adviser registration is: “Any person who does not hold herself or himself out to the general public as an investment adviser and has no more than 15 clients within 12 consecutive months in this state.” The de minimis exemption for federal covered advisers is: The investment adviser does not have a place of business located within Florida and has had less than six clients who are Florida residents during the preceding 12-month period. Please refer to Chapter 517.021(14)(b), Florida Statutes, and the Investment Adviser section on this website for additional information.
The catch phrase is "Any person who does not hold herself or himself out to the general public as an investment adviser." To market yourself or get paid out of the trading account, you need to be an RIA.