CE525 is a single pilot airplane. I seem to remeber that you had to have the following to fly it single pilot though.
Adequate storage space.. .Headset. .Operational Autopilot. .Cessna Abbreviated SP checklist. .Single pilot type rating ( ie no " SIC required " restriction on licence )
If one one was missing then a co-pilot was needed. Mind you I never had storage space on the airplane so F/O needed on allmost every flight. Gave a chance for a guy that had never got his hands on jets to log some time.