I came to them after I have the idea of the product. They will only pay attention to you if you are offering something of value to them. Doesn't work here the aproach "let's take a coffee and chat about your problems".

You don't have to have anything built, but you will pitch as your product is functional and tested. So they will answer questions regarding your concrete product, not an abstract idea.

If someone decide to buy, then you build what you promised. If not, you try to learn why.

Do you mind if I asked what is your idea?