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.
Nowadays making money from google Adsense with blogs very difficult because either your competitors or some people just copy your content and post it in either some useless blog for a backlink or in any other forum. Once content is duplicated then google search engine will punish the blog ranking and once you lose the blog ranking then automatically you lose the traffic and revenue. It is a continuous process of maintaining a blog and it can't be a passive income. You may not be investing money but need to invest your time to it.
I agree with you. Now it's very difficult to make money using google Adsense. They have very strict requirements. Although this could be a good source of income. But you will have to invest a lot of time and effort and maybe even money