E163: How Thiel Fellows Build Billion-Dollar Startups w/Zaid Rahman

Zaid Rahman is the founder and CEO of Flex, a breakout fintech startup that’s reinventing credit and payments for the middle market. Backed by the Thiel Fellowship and known for his “Delta 4” product philosophy, Zaid is building a multi-product platform that’s helping profitable, owner-operated businesses unlock capital and scale faster. In this conversation, Zaid breaks down how Flex is using AI to radically reduce underwriting time, why he’s obsessed with hiring 10x talent, and how “taste” and first principles thinking guide everything from product design to risk management. If you’re building in fintech, hiring in tech, or just obsessed with the craft of company-building, this episode is full of tactical insight. Highlights: The Delta 4 framework: how to build products people rave about Flex’s competitive edge vs. Brex, Ramp, and legacy banks How Flex slashed credit underwriting time from 25 days to 48 hours using LLMs Why Zaid believes fintech is “still day one” in 2025 How to spot first-principles thinkers in interviews (and why “best practices” is a red flag) Why Flex targets the “jumbo shrimp” of the middle market How Zaid built a 250+ member Thiel Fellow community from scratch The real cause of burnout—and how to build a sustainable high-performance culture -- Guest Bio: Zaid Rahman is the founder and CEO of Flex, a fintech platform serving mid-market businesses with credit, payments, and financial tools. A recipient of the prestigious Thiel Fellowship, Zaid previously founded multiple startups and is known for his rigorous hiring philosophy, taste-driven leadership, and commitment to building “Delta 4” experiences. Our Podcast now receives more than 300,000 downloads a month. Are you interested in sponsoring an episode? Please email David Weisburd at david@weisburdcapital.com . We’d like to thank @JuniperSquare for sponsoring this episode! #VentureCapital #VC #Startups #OpenLP #assetmanagement -- Sponsor: Juniper Square is dedicated to transforming the private markets investing experience. The company provides a full range of modern, connected fund technologies and services for over 2,100 private markets GPs across fundraising, reporting, fund administration, treasury, compliance, and business intelligence. Today, over $1 trillion of assets and 600,000+ LP accounts are managed through Juniper Square software and fund administration services. Learn more at www.junipersquare.com/vc . -- Stay Connected: X / Twitter: David Weisburd: @dweisburd Zaid Rahman: @zaidrmn LinkedIn: David Weisburd: https://www.linkedin.com/in/dweisburd/ Zaid Rahman: ​​ https://www.linkedin.com/in/zaidrahman/ -- Links: Flex: https://www.linkedin.com/company/flex-super-app/ -- Questions or topics you want us to discuss on How I Invest? Email us at david@weisburdcapital.com . (0:00) Episode preview (2:14) David Weisburd: Benefits of the Teal fellowship and creating a WhatsApp group for fellows (4:44) David Weisburd: Using AI for credit underwriting at Flex (8:14) David Weisburd: AI's impact on efficiency and differentiating Flex from competitors (11:36) David Weisburd: Recruitment strategy and identifying team members with good taste (20:59) David Weisburd: Evaluating candidate contributions and defining unique positions (24:44) Understanding customer priorities and the importance of first principles thinking (27:09) Learning through interviews and the challenge of finding the right hire (31:06) Balancing expertise and culture fit in hiring and the role of non-10x employees (38:23) Addressing burnout in a high-intensity work environment (40:54) The future of FinTech and Flex's vision (46:27) Closing remarks