Thanks Donna for taking the time to write this excellent comment. I agree with you 100%. A blog can give you an income from offline sources and is a great way of diversifying into different areas, but again it also depends on the niche you find yourself in. I always say to people to not be too reliant on one source of traffic or one source of income, because they can vanish pretty quickly.
If your niche doesn’t allow you to promote or build premium products (anything over around $100 per unit) then think about getting a solid mix of offerings and building it up over time. I remember Darren Rowse saying that initially Amazon Associates was a really small source of income but over the years it has really started to add up. Think eBooks, affiliates, consulting, books, etc. and you’re starting to build an income stream.
Once you setup your account on AdSense you will be given a code to add to your blog. This code will automatically display advertisements on your blog from companies who are part of Google’s advertising network. You may see ads from small companies related to your topic, or you may see ads from large companies that are completely unrelated to your topic.