Manga artist salary: Case Study of Satou Shuuhou

I have always wondered about a manga artist’s salary, and how does that artist earn a living. I believe that this is one big question to many people, and especially to aspiring manga “artists-to-be”.
After searching in Google and in many places, the answers provided are less than satisfactory.
However I chanced upon articles about Satou Shuuhou, the manga artist of Umizaru and Blackjack ni yoroshiku(seinen manga, which is for young adults and maybe unsuitable for teenagers), where he spoke about his distress with his publishers in his blog.
Subsequently, Satou Shuuhou reveals his income, expenses and some of his struggles as a manga artist. Now, he started to sell his manga online.
