You have a big assumption: Product X will be valuable enough that people in group Y will pay for it. Your way of testing that assumption is to spend 5 months coding plus N months trying to sell it.
So at the end of 6-12 months, suppose you discover that Product X is in fact not valuable. All of the coding time and a substantial portion of the marketing time will be wasted.
Ask yourself: what's the cheapest possible way to test your core assumption?
You have a big assumption: Product X will be valuable enough that people in group Y will pay for it. Your way of testing that assumption is to spend 5 months coding plus N months trying to sell it.
So at the end of 6-12 months, suppose you discover that Product X is in fact not valuable. All of the coding time and a substantial portion of the marketing time will be wasted.
Ask yourself: what's the cheapest possible way to test your core assumption?