Flutter Location-Based Q&A MVP

I’m building a real-time, location-based marketplace where anyone can ask “What’s happening right here, right now?” and get crowd-sourced answers from people nearby. The core workflow is simple: a user posts a question tied to a GPS point on Google Maps, nearby users receive a push notification, reply with text, photos, or videos, and the asker rewards the best response.

For the MVP I want a single codebase in Flutter targeting both iOS and Android, backed by Firebase services. Phone-number authentication will keep onboarding frictionless. Key features include:

• Geolocation map view and question pins
• Push notifications triggered by proximity radius
• Create questions, submit multimedia answers (text, photo, video)
• Rating system to choose the “best” answer and release the reward
• Simple in-app wallet to track funds and payouts
• Admin web panel for content moderation, user management, and basic analytics

Please outline:
1. Your recommended tech stack (Firebase modules, state management, any third-party libs)
2. Milestone schedule with timeframe to reach a testable build in one pilot city
3. Rough budget range and payment structure you prefer
4. Links or store listings of similar location-aware or marketplace apps you have shipped

I’ll supply UI wireframes, reward logic, and the initial city data set. Clean, well-commented code and Git version control are required so we can extend the product city-by-city after launch. I’m ready to start as soon as we align on scope and timeline.