MERN Stack Development Task

I need a skilled MERN stack developer to implement a fully designed application.

Key requirements:
- User authentication
- Real-time data updates
- Payment processing
- Integrate with multiple third-party services

Ideal skills and experience:
- Proficiency in MongoDB, Express.js, React.js, Node.js
- Experience with user authentication and payment processing
- Strong background in integrating third-party APIs
- Ability to work with existing designs and wireframes

Please provide past work examples and estimate.