I want to make a product, but I don't know which one.
Fatal mistake.
If you want to make something, your best ticket is to make something you know about.
So if you are into DayZ Gaming (example), then make a DayZ Forum.
If you are going into something just with the goal for making money wihtout previous knowledge and connections, you will fail.
For example, I can't make a mechanic forum because I don't know shit about that and I don't know people to get to the forum.