One of the most important reasons to blog first is the relationships within your niche that you will develop. You should be producing content that gets you noticed, and networking with other blog owners that have complimentary audiences.
This can get you links, which leads to traffic, subscribers and eventual buyers. But the relationships you establish have much more value than that. Those key people can also become your affiliates, joint venture partners, and a source for crucial pre-launch feedback and testimonials.
Recruiting quality people to sell your product for you is harder than many people think. But it’s a whole lot easier when you have built up credibility with your blog, well before you start selling anything.