I think the idea of going for startup starts with the risk. The risk of time, the efforts, failure and so on. No one can predict how the business will do in future and will it get proper validation from customers or not. Hence, one must be ready for the uncertainty that is inevitable in businesses. Even, for instance, it took Amazon more than 14 years to make the profit.
At the end, one must remember "The only thing certain about building a business is Uncertainty. "