Sarah Mausolf built Winnie, a $212 billion marketplace that connects parents with daycare and preschool providers across the United States. This is her story of going from MIT math major to Google product manager to startup founder, navigating the challenges of raising $9 million as a female founder in an 'unsexy' space, building supply before demand, and creating a platform that's become the default search tool for childcare. She shares the reality of cofounding while parenting through cancer, illness, and multiple pregnancies, the pivot from a failed Yelp-for-parents concept to a focused childcare marketplace, and why keeping the product free for parents while monetizing providers is the only model that makes sense.