Desktop Sales & Invoicing Tracker

I need a custom desktop application that lets me keep all sales-related data in one place. The core workflow should allow me to enter customer details, log every sale, generate an invoice on the spot, and come back later to pull reports that summarise totals, outstanding balances, and other key figures.

Ideally the program opens quickly on any modern computer, stores its data safely (local database is fine, but I am open to a lightweight cloud sync option if it adds little overhead), and exports reports or invoices to PDF or CSV so the figures can move straight into my accountant’s system. A clean, uncluttered interface is important because I’ll be in and out of the software all day.

For a smooth hand-off, please provide:
• A ready-to-run installer (Windows first; cross-platform is a plus)
• All source code with basic build instructions
• A short user guide that shows how to add a customer, record a sale, and issue an invoice
Once I can perform those three tasks and pull a monthly sales report without errors, I’ll consider the job complete.