I have an idea for a website that will attract many visitors.
I will need to put a lot of effort to build it,
but then it will run (almost) by itself.
What will be the best way to convert it to some passive income?
Advertising? Affiliates? VIP registration?
How much should I expect to earn from it?
I thought you have idea for a website that will attract visitors? The why are you asking for advice on how it would work. Better do it first then introduce it to the public and see whether it will attract them other not.