A fantastic article by Gwydion Suilebhan, with this advice:
If you want to be a playwright, get a second career, too. With the same passion you pursue writing for the stage, pursue something else. Something more lucrative, something you like, something the world clearly wants more of. (Because that’s sometimes hard to see about theater.) Make it your second-favorite profession, if you must, but make it something you expect to do forever, or at least until (like me) the next career comes along.