Just so you're aware in order to hold a professional license you will need to take a class 1 medical.
Not in the US, under Part 91, which covers corporate aircraft operations, one may act as a PIC and/or SIC in a corporate aircraft regardless of size, with a Second Class Physical.
Legally in the US, only if one is the PIC of a airline or charter aircraft is one required to have a First Class Physical.
By ICAO regulations, a US FAA Second Class physical is consider the same as a JAA First Class Physical. However, some countries still require a First Class Physical for
any pilot flying as PIC for remuneration, airline or corporate.
Simply put;
FAA First Class; Airline/Charter PIC.
FAA Second Class; Airline/Charter SIC/FE, Part 91 corporate PIC/SIC. (and ATC controllers)
FAA Third Class; Private Pilot privileges. (Not for hire under any circumstances.)