My Dad has been doing this. He retired at 55 and does this for a living now and over the course of the year has worked out that he earns around 4-500 a week doing this and has not had to draw on his pension yet.
He treats it like a job though and is meticulous in studying the form and the majority of his wins are now laying the favourites
That's not matched betting in the sense of this thread, it's a way to get money out of free bets that betting firms offer.
Fair play to him though, it must be a lot of work.