Gold Shop Billing and WhatsApp Automation System

Custom Gold Shop Billing Website with Secure Data Ownership & Backup Project Overview I need a private, secure billing website for my personal gold shop. This is not an e-commerce website and does not require a jewellery catalogue or online shopping facility. The system should help me create gold bills, manage customers, calculate charges, generate invoices, and share invoices through WhatsApp. Required Features - Admin login with secure password protection - Customer management with name, mobile number, and purchase history - Gold billing based on: - Gold weight in grams - Purity such as 22K and 18K - Gold rate per gram - Making charges - Wastage percentage - Other charges and discounts - Applicable taxes - Multiple items in one invoice - Automatic total calculation - Unique invoice number - Printable and downloadable PDF invoice - Paid, unpaid, and partially paid status - Invoice sharing through WhatsApp - Sales history and search facility - Daily, monthly, and yearly sales reports - Excel/CSV data export - Responsive design for mobile and desktop Data Security and Ownership — Very Important The website, domain, hosting, database, source code, customer records, invoices, and business data must belong to the client. - Domain and hosting must be created under my own email and account. - The developer must not host the website only under their personal account. - Automatic daily database backups are required. - I must be able to download complete backups whenever needed. - Customer, invoice, and sales data must be exportable in Excel/CSV format. - Full source code and database backup must be handed over after completion. - If the developer stops working or maintenance is discontinued, I must still retain access to my website and data. - The developer must provide complete handover and restoration instructions. - No data should be deleted, locked, or made inaccessible without my written permission. WhatsApp Integration The system should allow me to select a customer, generate the invoice PDF, and share it through WhatsApp. Please clearly explain whether official WhatsApp Business API, a third-party provider, templates, or additional message charges will be required. Developer Requirements Please include the following in your proposal: 1. Total project cost 2. Development time 3. Technology stack 4. Previous billing or business-management projects 5. Hosting and deployment method 6. Backup and data-recovery process 7. WhatsApp integration method and additional charges 8. Yearly hosting and maintenance cost 9. Support period after delivery 10. Confirmation that full source code and data ownership will be provided Please provide a working demo of the billing calculation, invoice PDF generation, backup system, and data export before final delivery.