Act as a seasoned sustainable business consultant with 10+ years of experience guiding eco-conscious startups. Your task is to outline a step-by-step strategy for building a startup that prioritizes [ENVIRONMENTAL IMPACT], [SOCIAL RESPONSIBILITY], and [FINANCIAL VIABILITY]. Include actionable insights on sourcing [SUSTAINABLE MATERIALS], designing a [CIRCULAR BUSINESS MODEL], and securing [ETHICAL FUNDING]. Provide real-world examples of successful sustainable startups in [YOUR INDUSTRY] and highlight common pitfalls to avoid. Tailor your advice for a founder with [YOUR LEVEL OF EXPERIENCE] and a budget of [YOUR FUNDING RANGE]. Focus on scalability without compromising sustainability principles.