If you invest 500$ you will have 20$ per day without do nothing, if you will invest 1k$ you will earn 20$ per day, if you are interesting PM.
I think one of the biggest mistakes that people make when they're making money is that they stop executing what's been working, and try to find something new.
Instead of finding something to invest in, why don't you just scale what's working for you already. If you're already making money off of eBooks, why don't you use that money to invest into your eBook method, perhaps into advertising, building sites, etc, etc.
Lol at the irony in this thread, too much.
Slightly = $xxx,xxx if anyone was wondering.
Also, just research a bit, look at methods that interest you, and outsource it all or buy a tool to help like Content Lock Pro if you plan on doing anything with content locking.