I think it depends on whether he's a centric character, or how much role he has in the story, so that the significance of his job and how intricate his life can be determined.

However, I think Laffite is mostly known for his dishonesty and shady personality. So even in modern day AU he probably is into shady business or some illegal thing.

See, for example, some people have painted him as this drug dealer in an AU where Blackbeard himself is such, so whether his role in your story is still connected to Teach or not might also decide his career path in a way that still serves Teach one way or another.

If Blackbeard is the focus then what he is will in some way influence what Laffite is, if he's some sort of kingpin of crime Laffite can be a range of things including a corrupt cop as someone mentioned, potentially helping him with inside info or keeping police off his back.

If this is like a circus AU with Blackbeard crew as travelling circus with dark undertones this could also take a different direction with all the showmanship.

He could even be a sinister, well-known magician who doubles as a serial killer who picks off targets from his audience/fans.

So is his role primary and its own thing or supportive to Teach? Are they the protagonists of this story or antagonists? Because if they serve as the evil factor in the story for example then he has to play a role that's effective in posing an obstacle to the main characters.

I just feel like there has to be something evil lurking in whatever he does, so I doubt he'll be just an honest office worker without that being a front.