The author actually believes (or writes) you can start a photography business with a $400 initial investment.
... but it doesn't have to be a wallet buster. You can find a good, used 35mm snapper—with lens—for between $75 and $300 (new ones start around $150 and go on up — way up—from there). Larger-format, 2-1/4 cameras usually cost somewhere between $100 and $300 used (while new ones start at $300).
I sure would like to know where you can get a good 35mm camera for $300! I spent over $15,000 this year on 35mm cameras and I only got two of them!