First of all you have to decide what kind of site you will make. I am not going to share with you my ideas for that 
but you have to be on a wave and see what people need today. Only that will make your site super popular fast and will bring you first profit fast as well.
but you have to be on a wave and see what people need today. Only that will make your site super popular fast and will bring you first profit fast as well.Well sharing is caring. If you have good ideas, you can share with others so people can get benefit. For me you can create your own blog of your interest and once you feel it is little popular you can apply google adsense ads to earn from them.
I agree with you, the blog should be very interesting for a lot of people. And in order to make it interesting, you need to invest a lot of effort into it. That's why it seems to me that this can not be called a passive income.