See the thread titled “Gulfstream IV SIC” this folder. Galaxy Flyer’s post #4 sums it up nicely.

Private, AMEL and Instrument Rating, Appropriate ground and flight training and basic aircraft familiarity per 61.55. No BE-300 SIC Type is required for domestic US airspace ops.

Ask yourself- Do You want that SIC to just sit on their hands/work the radios, or be a relevant and trained member of the flight crew in the event of an emergency?