It sounds like you have already made your mind up subconsciously to give it away for free. If you put it up on your site and it is popular and generates a lot of traffic for you, you will make money in the long run anyway.
I manage a gym in Bangkok and am a also a personal trainer and I thought about doing the same as you, selling an ebook of material I had written on health and fitness. However I decided to set up a website and put all that information plus more and my traffic has gone nuts in less than 5 months online.
Keep writing and learning along the way, the right answer will come to you. My link is below.