There is no answer to this question, because the answer is always individual. Some startups seek to recoup their investment already at the product launch stage. Others, such as Facebook, may not start the monetization process for years, but at the same time the company’s shares will skyrocket in price, and the company’s value is estimated higher than General Motors. Consult with financiers, do business analysis, consult with your investors and write a business plan. Everyone will have their own.