One of the most exciting things a startup CEO in a business-to-business market can hear from a potential customer is, \u201cWe\u2019re excited. When can you come back and show us a prototype?\u201d\n\nThis can be the beginning of a profitable customer relationship or a disappointing sinkhole of wasted time, money, resources, and a demoralized engineering team.\n\nIt all depends on one question every startup CEO needs to ask.