Multiplatform Marketplace App Development

I want to launch a simple yet reliable buy-and-sell app that works on both iOS and Android. Users will be able to list brand-new, pre-owned, and even refurbished items, then choose whether the deal happens through local pick-up or postal delivery.

Key flows I need covered include:
• Quick registration via Gmail sign-in or mobile number OTP verification (no lengthy forms).
• A clean catalogue where sellers upload photos, set prices, and flag listings as “pick-up” or “post.”
• Two payment paths—online checkout (any standard gateway is fine) or cash handed over in person.
• A “Chat on WhatsApp” button that opens a direct conversation between buyer and seller for last-minute questions.

Because this is a small operation, the build should stay lean: a single codebase (Flutter or React Native is perfect), a lightweight admin console where I can suspend users or edit listings, and straightforward deployment to both app stores.

Deliverables I expect
– Full source code with clear setup instructions
– iOS and Android release builds, ready for TestFlight / internal testing
– Basic web-based admin panel
– One short hand-off session walking me through publishing and day-to-day maintenance

If something in the feature list looks unclear, just point it out and we can adjust before you start coding.