Principle 4 of 11
Know What You Own: How Does a Company Make Money?
Invest in what you understand. Know how a company actually makes money.
Know What You Own in one sentence
Knowing what you own means you can explain, in plain words, how a business makes money before you ever think about investing in it.
A famous rule among investors goes something like this: if you can't explain what a company does to a friend in two sentences, you probably don't understand it well enough to own it. A stock ticker is not just a symbol that moves up and down — behind it is a real business with customers, costs, and (hopefully) profits.
Example: the juice stand
Let's look at the simplest business there is: a juice stand. Each cup sells for $2. The cup, the fruit, and the ice cost about $0.50 per cup.
| Per cup | 40 cups | |
|---|---|---|
| Revenue (money coming in) | $2.00 | $80.00 |
| Costs (money going out) | $0.50 | $20.00 |
| Profit (what is left) | $1.50 | $60.00 |
That is the whole idea: revenue minus costs equals profit. Every company — from a juice stand to a giant tech company — runs on this same math. Some earn money by selling products, some by charging subscriptions, some by showing ads, and some by taking a small fee every time someone pays.
Why it matters
When you understand how a business makes money, the news starts to make sense. If you know a company earns most of its money from subscriptions, a headline like "subscribers dropped this quarter" suddenly matters. If you don't know, it is just noise.
Understanding what you own also helps you stay calm. People who don't know why they own something tend to sell in a panic the moment the price drops. People who understand the business can ask a better question: did anything actually change about how this company makes money?
Before owning any investment, try answering these questions:
- Who are the customers?
- What do they pay for?
- What does it cost the company to provide it?
- Why would customers keep coming back instead of going to a competitor?
Common mistake: owning a name, not a business
Lots of people want to invest in a company just because they like its products or have heard its name a lot. Liking a product is a fine place to start your research — but it is not the same as understanding the business. A brand everyone loves can still lose money if its costs are higher than its revenue.
Check yourself
1. A bake sale sells 30 cookies at $1 each. Ingredients cost $9 total. What is the profit?
Show answer
$21. Revenue is 30 × $1 = $30, and $30 − $9 = $21.
2. What is the difference between revenue and profit?
Show answer
Revenue is all the money coming in from customers. Profit is what is left after paying the costs.
3. Name two different ways a company can make money.
Show answer
Any two of: selling products, charging subscriptions, selling ads, charging fees on transactions, renting things out, providing services.
Try it: Match the Company
Match the Company is a Daily Challenge game where you match well-known companies to how they actually make money. Match well-known companies to how they really make money — it is this principle, turned into a game.
Learn one of these every morning
Market Juice is a free daily digest for kids ages 10–16: real market news, three quick games, and a lesson that ties back to these principles — about 3 minutes a day.