As there is little to no information about how one achieves the rank of a professional go player (in Japan at least), perhaps someone who knows could expand this page a little?
You have the last years Honsen here: http://www.nihonkiin.or.jp/saiyo/2012/honsen.htm
But I guess it is important to mention that only 2 players qualify via the Honsen, while 1 via the female Honsen, 1 as the first placed insei, 2 more from the branches. So you arrive at 6 new Nihon Ki-in professionals per year and the Honsen doesn't even provide the majority of them. Slightly less players qualify through a completely different system in the Kansai Ki-in.