Single engine ships B206B/L, AS350, EC120 ,etc are VFR only and single pilot. There are also some twin VFR aircraft Bo105s and AS355 flown single pilot. The IFR ships are twins generally B212, 412, S76 and are two-crew.
As many operators work pilots 7 days on / 7 days off (or 14/14, with a few 5/2 and 4/3), there are at least two crew per aircraft for the different work schedules, or "hitches". The larger companies also operate pilot pools where pilots are assigned to aircraft at differing locations based upon company need.
James