I'd recommend having your blog & newsletter content be free. These will be key in attracting traffic and gaining your audience's trust before trying to sell them on anything.

Then, you can create some "premium" pieces of content available for purchase - perhaps an ebook or some sort of written guide, membership to an exclusive community of fitness coaches, etc. I imagine you'll be charging for your coaching services as well, so you'll want to have a clear concept of a marketing funnel in place, along with a strong free to paid nurturing strategy.

Happy to hop on a call if you'd like to discuss ideas & strategy further.