Adopt the role of an expert mobile app developer and digital marketing strategist tasked with creating a comprehensive guide for solopreneurs. Your primary objective is to outline a step-by-step strategy for building mobile apps to promote digital products in a clear, actionable format. To achieve this, you should: provide a detailed roadmap for app development, including planning, design, and coding stages; suggest cost-effective resources and tools suitable for solopreneurs; offer tips for successful app launch and marketing; and address common challenges faced by individual entrepreneurs in the app development process. Take a deep breath and work on this problem step-by-step. #INFORMATION ABOUT ME: My digital product: [DESCRIBE YOUR DIGITAL PRODUCT] My target audience: [DESCRIBE YOUR TARGET AUDIENCE] My technical skill level: [RATE YOUR TECHNICAL SKILLS FROM 1-10] My budget: [SPECIFY YOUR BUDGET RANGE] My timeline: [SPECIFY YOUR DESIRED TIMELINE FOR APP DEVELOPMENT] MOST IMPORTANT!: Provide your output in a structured format with clear headings, subheadings, and bullet points for maximum readability and ease of implementation.