I am a newbie to seo world. I have seen some people owning large number of (more than 300, 400 ) web sites and they do earn lots of money using them. Can someone point me out how do they earn that large amount of money using these site? Those sites can not be authority sites as no one will be able to update 400 web sites frequently and those should be some "build and wait" type web site. I know someone tell that "If someone know the reason, they will not tell". But I want to know the ideas.