🌱 A plan for a young person: an index core and a small trading satellite

🎯 In 30 seconds: Put your money in order: a cash emergency fund first, then a "core" of low-cost, broad index funds that you add to every month and leave alone, then a small "satellite" for active trading that is capped at a set share of your money. Starting young matters more than almost anything else, because compounding needs time. If you earn money from a job, a Roth IRA can hold your core and let it grow tax-free. The satellite is where you learn, and it is sized so that losing all of it would not change your life.

The order of operations

Before any investing or trading, line up these steps. Each one protects the next.

1. Emergency fund. Cash in a savings account for surprises: a phone repair, a car problem, a gap between jobs. The CFPB says the right amount depends on your situation. A practical starting target for a student is a few hundred dollars, growing toward one to three months of your own costs once you live on your own.
2. No high-interest debt. Paying off a credit card that charges over 20% is a guaranteed return no investment can promise. See the debt tool.
3. Core. Regular deposits into broad, low-cost index funds, held for decades.
4. Satellite. A small, capped amount for trading and learning.

The emergency fund and budget tools help with steps 1 and 2.

The core: boring on purpose

The core is a fund that holds hundreds or thousands of companies, like an S&P 500 index fund or a total US stock market fund, often with an international fund alongside. You buy it on a schedule, for example the same amount every payday, no matter what the market is doing. Buying a fixed dollar amount on a schedule is called dollar-cost averaging.

Three things make a good core fund:

• Low cost. The expense ratio is the yearly fee as a percentage of your money. Broad index funds with fees well under 0.10% a year are common. A 1% fee takes a large bite over 40 years.
• Broad. Many companies across many industries, so no single failure can sink you. See Diversification and correlation.
• Simple. One to three funds is enough. ETFs and index funds explains how they work.

The core will fall in bear markets, sometimes by a third or more. The plan is to keep buying through those, not to sell. Bull and bear markets shows how past declines played out.

Why starting early matters: a worked example

Compounding means your returns earn returns. The longer the money sits, the more of your final balance comes from growth instead of deposits.

Two hypothetical savers. Both invest $100 a month and earn a steady 7% a year, compounded monthly. That rate is an assumption for teaching, not a forecast. Real returns vary a lot from year to year, can be negative for years at a time, and inflation reduces what the dollars buy.

• Ana invests from age 16 to 26, then stops adding money. She puts in $12,000 in total.
• Ben starts at 26 and invests every month until 67. He puts in $49,200 in total.

The same $100 a month, started at different ages and held to 67, at the same assumed 7%:

The formula behind the table, for a monthly deposit D, monthly rate r (7% / 12) and n months: balance = D x ((1 + r)^n - 1) / r. You can check any of these numbers with the SEC's free compound interest calculator on Investor.gov.

A Roth IRA if you have a job

An IRA (individual retirement arrangement) is an account with tax benefits. In a Roth IRA, you put in money you have already paid tax on, and qualified withdrawals in retirement, including all the growth, are tax-free.

The rules that matter for a young person, from the IRS:

• You need earned income. Money from working: wages, tips, or net earnings from your own small business. Allowances, gifts and investment income do not count.
• There is no minimum age. The IRS rules say you can contribute to a Roth IRA at any age if you have compensation.
• The limit for 2026 is $7,500, or your taxable compensation for the year if that is less. A teen who earned $3,000 at a summer job can put in up to $3,000.
• Your contributions can come back out. Under IRS ordering rules, withdrawals from a Roth IRA come from your regular contributions first, and those are not taxed. Earnings withdrawn early can be taxed and penalized, so treat the account as long-term money.

Most brokers require an adult to open a custodial Roth IRA for anyone under the age of majority in their state. Account types explains custodial accounts and what changes at 18 or 21.

The satellite: how much to trade with

The satellite is money you are allowed to lose. Use it to practise the skills in this course with real orders and real emotions, at a size that cannot hurt your future.

Rules that keep it small:

1. Set a cap. For example, 10% of your invested money, or a fixed dollar amount like $500. Write it down.
2. No refills from the core. If the satellite drops to zero, you can refill it once a year from new savings, not by selling core funds.
3. Trim winners into the core. If the satellite grows above its cap, move the excess into the core.
4. Per-trade risk stays small. Even inside the satellite, risk 1% to 2% of the satellite per trade. See Risk comes first.
5. No leverage until you have a record. At least a year of journaled trades showing positive expectancy before margin, futures or selling options. See Leverage everywhere.

A worked first year, with hypothetical numbers

Jordan is 17 and earns $6,000 from a summer and weekend job.

Jordan uses the $300 to buy a few fractional shares with planned stops, and logs every trade in a trading journal. Where to hold the satellite is a choice: inside the Roth, gains are not taxed but losses cannot be deducted. In a regular custodial account, gains and losses go on the tax return. Taxes for traders covers this.

Try it

1. Use the goals tool to set an emergency fund target.
2. Write down your core fund choice, monthly amount and the day of the month you will invest.
3. Write down your satellite cap in dollars and the three satellite rules you will follow.
4. Open a paper portfolio with your satellite amount and trade it for a month before using real money.

Sources

• IRS: 401(k) limit increases to $24,500 for 2026, IRA limit increases to $7,500
• IRS: Publication 590-A, Contributions to IRAs
• IRS: Publication 590-B, Distributions from IRAs
• CFPB: An essential guide to building an emergency fund
• Investor.gov (SEC): Compound interest