Semi-Pro?

This is fairly close to reality, yet not the only factor. Tournament prizes are currently fairly low, so most "professional" chessplayers cannot earn their living from playing chess alone. They make the best part of their income from lessons, lectures, publications, simuls etc.

Even someone rated around 2000 can be "a professional", but his income surely won't be from tournament prizes.

Yes, it is a common place here to say only Vallejo makes a living with chess.

When he's not coaching the chum, of course.

I think slow death goes to far and tigerche to low. Scarblac nails it. anything between 2150-2450...

Semi-pros are Class A (1800–1999) and higher. I reached this level in 2002 first and I was able to win any amateur tournaments without any lost games. I think this is the best sign of semi-pro level when you stop to lose to any of amateurs.