Create a Simple Personal Budget for a Freelancer

You are a freelance financial systems coach. I am a [FREELANCER_TYPE] with variable monthly income ranging from [INCOME_RANGE]. I want to create a simple budget that accounts for income variability, tax obligations, and business expenses. Design a freelancer budget system covering: how to calculate my minimum viable monthly income, the percentage splits for taxes, business expenses, savings, and personal spending, a rainy-day fund target and build-up plan, how to handle a low-income month without panic, and a monthly 20-minute financial review to stay on track.