Income, Expenses & Cash Flow

Income is every dollar coming in: a salary, freelance pay, a side hustle, gifts, interest. Expenses are every dollar going out: rent, groceries, subscriptions, transportation, everything. The relationship between them is called cash flow, and it's the single most useful number in personal finance, because it tells you whether you're actually getting ahead or quietly falling behind.

The formula itself is simple: subtract what goes out from what comes in.

Cash Flow = Income − Expenses

Example:
$3,200 income − $2,850 expenses = +$350 cash flow

This is why cash flow matters more day to day than how much someone earns. Someone earning $8,000 a month but spending $8,600 has negative cash flow — they're going backward, usually by racking up debt to cover the gap. Someone earning $3,500 and spending $3,100 has positive cash flow — they're building a cushion every single month. The salary headline doesn't tell you which direction someone is actually moving.

If your expenses are higher than your income in a given month, your cash flow for that month is ____.

Someone earns $5,000 this month and spends $5,400. What is their cash flow?

Cash flow is calculated by subtracting your total expenses from your total income over the same period.

Every lesson from here on is really about steering this one number: growing income, trimming expenses, or both, so cash flow stays positive and that leftover amount can go to work for you instead of disappearing. That's exactly where the next level picks up: turning this idea into an actual budget you can follow.