Great article by poker pro Mark Gregorich for anyone thinking about going pro. Net-net, its a hard road, not the fun and games it may look on TV.
As an aside, I've played with a bunch of "name pros" at this point and Mark is one of the coolest guys I've met. You can find him playing 100-200 most days at Bellagio and you won't find a nicer guy. He'll take all your money with a smile.