Subject to the provisions of this Part, a person shall not carry on business, or hold himself or herself out as carrying on business, as—
(a) a broker dealer;
(b) a limited service broker;
(c) an investment adviser;
(d) a custodian;
(e) a principal of a broker dealer, limited service broker or corporate investment adviser; or
(f) a representative of a broker dealer, limited service broker or investment adviser,
unless the person is licensed to do so by the Commission under this Part.