Full-Stack Team Needed For Online Marketplace, Admin Portal, API Integrations, Ongoing Maintenance

We are looking for an experienced full-stack developer or small development team to help take an online marketplace platform from prototype/planning into a launchable production MVP. The project is a multi-sided marketplace with a public shopping/quote flow, customer account area, admin operating portal, data import workflows, offer or pricing comparison logic, API integrations, email/CRM workflows, and ongoing maintenance after launch. We already have product requirements, market/competitor research, UX direction, prototype screens, data-model planning, and operating workflow notes. We are looking for a team that can review the existing work, estimate the remaining build, and help us productionize the platform in phases. Initial scope: Review existing prototype, requirements, and data/API plan. Build or refine the responsive public marketplace experience. Create customer portal/account workflows. Create admin portal workflows for leads, customers, imports, offer/pricing data, operational status, and reporting. Build backend APIs and database schema for marketplace entities, users, offers/pricing records, source/version records, transactions, and audit logs. Support spreadsheet or matrix-style pricing/import workflows with validation, approval, versioning, rollback, and revalidation before checkout/submission. Integrate third-party APIs where available. Add email/CRM automation and AI-assisted internal workflow support where appropriate. Support checkout/enrollment or transaction handoff workflows. Add authentication, roles, validation, error handling, logging, QA, and deployment support. Provide ongoing maintenance after launch. Technology preferences: React/Next.js or similar modern frontend. Node/TypeScript backend preferred. PostgreSQL/Supabase or similar relational database. Vercel or comparable cloud deployment. Experience with API integrations, data imports, marketplace/ecommerce workflows, admin dashboards, authentication, and secure handling of customer data. Please propose: Estimated cost and timeline for a 60-90 day launchable MVP phase. Estimated cost and timeline for the broader full build. Recommended team composition and hourly rates. Monthly maintenance/support retainer after launch. Assumptions, exclusions, and risks. Examples of similar marketplace, portal, admin dashboard, API integration, or pricing/data-import projects. We are open to fixed-price milestone proposals or a capped time-and-materials engagement. We care more about clear scoping, strong architecture, and reliable execution than the lowest hourly rate.