Index Funds for Beginners: How to Start Investing With $100
You don't need a lot of money, a finance degree, or a stock-picking talent to invest well. For most people, the smartest approach is also the simplest: low-cost index funds.
What is an index fund?
An index is just a list of investments that tracks a slice of the market — for example, the S&P 500, which represents 500 of the largest U.S. companies. An index fund is a single investment that holds a little of everything in that index. Buy one share of an S&P 500 index fund and you instantly own a tiny piece of hundreds of companies at once.
That's instant diversification. Instead of betting on one company and hoping it does well, you own the whole basket. If any single company stumbles, it's a small fraction of your holdings. Index funds come in two wrappers — mutual funds and ETFs (exchange-traded funds) — that work similarly for a long-term investor; ETFs trade like stocks throughout the day, while mutual funds price once daily.
Why index funds beat most professionals
It sounds too good to be true that a "set it and forget it" fund could outperform highly paid experts, but the data is remarkably consistent: over long periods, the large majority of actively managed funds fail to beat their benchmark index after fees. Picking winning stocks consistently is extraordinarily hard, and the fees active managers charge create a constant drag. By simply owning the whole market at rock-bottom cost, index funds quietly outperform most of the people trying to beat them. This is why investors from beginners to Warren Buffett have recommended low-cost index funds for ordinary savers.
Why fees matter more than you think
A fund's expense ratio is the annual fee, expressed as a percentage of your investment. It sounds trivial — what's the difference between 0.03% and 1%? Over decades, it's enormous, because the fee compounds against you every year. On a long investment horizon, a 1% fee can quietly consume a large share of your potential gains compared with a near-zero-cost index fund. The rule for beginners is simple: favor broad index funds with very low expense ratios (many are well under 0.10%) and be skeptical of anything charging 1% or more.
Common types of index funds
| Fund type | What it holds | Role in a portfolio |
|---|---|---|
| S&P 500 index fund | 500 large U.S. companies | Core U.S. stock exposure |
| Total U.S. stock market fund | Nearly all U.S. public companies | Even broader U.S. exposure |
| Total international stock fund | Companies outside the U.S. | Global diversification |
| Total bond market fund | A broad mix of bonds | Stability / lower volatility |
| Target-date fund | A ready-made mix that shifts over time | All-in-one, hands-off option |
Many beginners do perfectly well with just one or two funds — a total U.S. (or S&P 500) fund, optionally paired with an international fund and some bonds as they get closer to needing the money. A target-date fund bundles all of that into a single purchase and rebalances automatically, which is ideal if you want the simplest possible setup.
How to buy your first index fund
- Choose where to hold it. If you're investing for retirement, an IRA or workplace 401(k) gives you tax advantages. For other goals, a regular taxable brokerage account works.
- Open an account with a reputable, low-cost broker. The process takes minutes and most have no minimum to open.
- Transfer your money — even $100. Note that cash sitting in the account isn't invested yet.
- Buy a broad, low-cost index fund. Search for a total-market or S&P 500 index fund or ETF and place the order. Many brokers now allow fractional shares, so $100 is plenty to start.
- Automate and repeat. Set up an automatic monthly investment. Buying steadily over time — "dollar-cost averaging" — removes the temptation to time the market.
Beginner mistakes to avoid
- Waiting for the "perfect" time. Time in the market beats timing the market. Starting now with a small amount beats waiting for certainty that never comes.
- Panic-selling when markets drop. Downturns are normal and temporary for a diversified, long-term investor. Selling locks in losses.
- Chasing last year's hot fund or stock. Past performance doesn't predict the future, and hot funds often come with high fees.
- Investing money you'll need soon. Money for the next few years — or your emergency fund — belongs in a savings account, not stocks.
- Forgetting to actually invest the cash. Depositing money is not the same as buying a fund. Place the trade.
General educational information, not investment advice. All investing involves risk, including possible loss of principal. Past performance does not guarantee future results. See our disclaimer.