job
Depends on how destitute you become playing chess.
On a serious note, you have to be a really good GM to etch a living playing tournament chess.
Some GM's will start a chess club and hope they can make a living out of that. The lucky ones might land a job at a school or college.
The rest try to play some tournaments and teach chess as a hobby that supplements their day job. A few pump out training material through a variety of ways and get royalties from the training material. I imagine that is a decent way for some extra income, but they have to keep pumping out new material to keep a steady flow of income coming in.