How do you know if Niche is Profitable

As the title suggests, this is my exact question. I cant seem to get the answers so any advice is great.

How do you know if the niche is profitable? I'm aiming for the amazon route of searching products but I'm not sure which product group or niche would be good.

Do you go with a product with a lot of high search keywords related to your niche? Do you go with products youre sure has competition or low ranking competition?

Really whats the thought process that will make you pick a…

How do you know if Niche is Profitable