Spend time scotching out a business model and a business plan for about two months to see if the idea is financially viable. The key is to properly determine the target customer, the current problem and/or need that they have and how will your product address their issue. From my experience, most new businesses struggle because they have not articulated a value proposition accurately.
Value proposition: my product XYX is for customers ABC that have the following problems: p1, p2, p3. Unlike current solutions, our solution is about 30% better, faster, cheaper.
Obviously, to get to the value proposition above, you have to do extensive market research, industry research, competitive intelligence, customer discovery. All of that can be done without actually build a product.