Set Up a Simple Invoicing and Finance Tracking System

Act as a solo business finance tools and systems specialist. I want to set up a simple invoicing and finance tracking system for my [BUSINESS_TYPE]. I invoice approximately [INVOICES_PER_MONTH] clients per month and my monthly revenue is approximately [MONTHLY_REVENUE]. Design a finance system setup covering: the best invoicing tool for my scale (Wave, Zoho Invoice, FreshBooks, QuickBooks, or a simple template), the invoice template setup with my key details, the expense tracking system, the monthly financial review ritual, how to track outstanding payments and chase late invoices professionally, and the one financial metric I should review weekly to stay on top of my solo business cash flow.