Is selling in Amazon a viable source of income now?

My question is, is selling on amazon a good source of making money? Do not worry I haven’t been influenced by gurus that says it makes millions easily and fast!!!!

I want to know if it can generate decent income. I have a couple questions.

What would ALL my initial costs be? Including everything and what is everything?

How would i go about doing it? I don’t wanna watch fake gurus, so whats a good way of learning the trade.

Thanks in advance!