The old way of building a business: have an idea, build it, market it, customers come rushing in. In this new age, we are in, this just doesn't work anymore. The new-age business roadmap is: have an idea, solve for your three assumed variables, build the idea based on these variables, customers actually come rushing in! 

Diana Kander's book All In Startup: https://amzn.to/2GHjUyX 

Learn about 1Swipe: https://cwadmail.wixsite.com/1swipe