Robert Kiyosaki is undeniably an expert on the subject of Cashflow.
His books include:
Rich Dad, Poor Dad (Rich Dad Poor Dad)
Cashflow Quadrant
Retire Young Retire Rich
Financial IQ

And many more.

His Educational board game "Cashflow 101" was closely followed by "cashflow 202" and is now available to play online in an e format.
The game serves to educate and entertain and is the fastest way I have seen (personally) to get an understanding of Cashflow and a balance sheet.
You learn what to look for in when buying assets, and how to make a decision if they are an asset or a liability.
You learn what you need to do in order to put real money in your pocket and to stop those liabilities that take money out of your pocket.
Highly reccomended.

Robert Kiyosaki is a wealth of knowledge and his teachings are insightful and easy to follow
You can go to his home page here: Robert Kiyosaki