I run a used-mobile store and need a single system that keeps every part of the business in sync. The core of the job is to build a functional prototype—web-based or lightweight desktop—where I can record, search, and report on everything that passes through the shop. The system must let me: • Register each phone with model, full specs, current condition, purchase price, expected selling price, and a scannable IMEI bar code. • Maintain real-time stock levels for phones, scrap units, phones under repair, and accessories. • Capture customer personal details, complete purchase / sale history, and set credit-payment reminders. • Generate invoices, print or email bills, and log daily expenses automatically into a profit-and-loss view. • Flag any handset that has been in inventory for more than a month so I can act on slow movers. • List outstanding credits and send follow-up reminders. • Offer quick reports: daily profit & loss, stock valuation, phones sent for repair, scrap value, accessories on hand. I am happy with any robust tech stack so long as barcode scanning for IMEI works smoothly and the UI is clean and fast. Data export to Excel or CSV is essential; cloud backup or simple local backup is highly preferred. Deliverables include the working prototype, database schema, brief setup guide, and two rounds of minor refinements after initial hand-off.