I must confess that I once did this myself. I wrote a book on how to make money when in actual fact I was hoping to make money through sales of the very same book. Sadly, when I did get a chance to run my own business, I failed. Sales of the boo were good but not as I would call myself a successful author.
There are so many that are like me online. The reason it is easy for them (us) is because we live worlds apart and you cannot pin me down for something I tell you about as you are not close by to see for yourself. The best person to teach on something is someone who has gone through the same and made a success out of it.
Just a warning.