You need a brokerage account, money to invest, and about 15 minutes to set up

To invest in an index fund, you open an account at a brokerage firm, transfer money in, and place an order to buy shares of the fund you choose. The entire process takes less than an hour for most people. You do not need a large sum to start — many brokerages let you begin with $1 or $100, though some have minimums of $500 to $3,000 depending on the fund itself.

The brokerage holds your money and executes your trades. Common brokerages include Fidelity, Vanguard, Charles Schwab, E*TRADE, and Robinhood. Each charges different fees and offers different funds, so the one you pick affects how much you pay and what options you have. Your choice of brokerage matters more than your choice of index fund, because you will use that account for years.

This guide walks you through picking a brokerage, opening the account, funding it, and placing your first order. It assumes you have a bank account and a way to verify your identity online.

Key Takeaways

  • You must open an account at a brokerage before you can buy any index fund, and the brokerage you choose determines what funds are available and what fees you pay.
  • Most brokerages let you open an account online in 10 to 15 minutes using your Social Security number, address, and employment information.
  • You fund your account by linking a bank account and transferring money, which usually takes one to three business days to arrive.
  • Once money is in your account, you search for the index fund by its ticker symbol, decide how many shares to buy, and place the order in seconds.
  • Index funds trade during market hours (9:30 a.m. to 4 p.m. Eastern time on weekdays), and your order executes at the price when the market closes that day.

Choosing a brokerage that fits your needs

Start by comparing three things: the funds they offer, the fees they charge, and whether they have a minimum account balance. If you plan to invest $500 or less to start, avoid brokerages with high minimums. Fidelity and Charles Schwab have no account minimums and no trading fees for most index funds. Vanguard has a $3,000 minimum for most of its own index funds but charges no trading fees once you are in. Robinhood charges no fees and has no minimums but offers fewer index funds than the others.

Check whether the brokerage charges a management fee or advisory fee if you use their robo-advisor (an automated service that picks funds for you). These fees range from 0.25% to 0.50% per year and are separate from the fund's own expense ratio. If you are picking your own index fund, you avoid this fee entirely.

Look at the specific index funds the brokerage offers. Most brokerages carry the major ones — S&P 500 index funds, total stock market index funds, and bond index funds — but the exact fund names and expense ratios vary. Write down the ticker symbols of two or three funds you are interested in, then check whether each brokerage carries them.

Opening your account online

Go to the brokerage's website and click "Open an Account" or "get your free guide." You will answer questions about your name, address, date of birth, Social Security number, employment status, and annual income. The brokerage uses this information to verify your identity and comply with federal regulations. The process takes 10 to 15 minutes.

You will be asked whether you want a taxable brokerage account or a retirement account (IRA or 401(k)). If you are investing money you do not plan to touch for decades and you have not maxed out retirement account contributions, choose a retirement account — the tax benefits are substantial. If you are investing money you might need within five years, or if you have already contributed the maximum to retirement accounts, choose a taxable account. Most people starting out should choose a taxable account because it has no withdrawal restrictions.

After you submit your information, the brokerage will show you a confirmation page with your new account number. Some brokerages fund your account when ready; others wait one business day. Check your email for a welcome message with login instructions.

Linking your bank account and transferring money

Log into your new brokerage account and look for "Transfer Funds," "Deposit," or "Link Bank Account." You will enter your bank's routing number and your account number, which you can find on a check or in your bank's app. The brokerage will make two small test deposits (usually under $1 each) to your bank account within one to two business days. You then log back into the brokerage and confirm the amounts of those deposits to verify you own the bank account.

Once your bank account is verified, you can transfer money. Most brokerages let you transfer up to $10,000 or $25,000 per day, though this varies. The money usually arrives in your brokerage account within one to three business days. Some brokerages offer next-day transfers for an extra fee.

Do not worry if the transfer takes three days. The market will still be there. Many new investors rush to invest as soon as they open an account, but waiting a few days to make sure you understand what you are doing is worth it.

Finding and buying your first index fund

Once money is in your account, log in and look for "Trade," "Buy," "Invest," or "Search Funds." Enter the ticker symbol of the index fund you want — for example, VOO for Vanguard's S&P 500 ETF, or VTSAX for Vanguard's Total Stock Market Index Fund. The brokerage will show you the fund's current price, expense ratio, and performance history.

Decide how many shares you want to buy. If the fund costs $100 per share and you have $1,000 to invest, you can buy 10 shares. Some brokerages let you buy fractional shares (for example, 10.5 shares), which means you can invest an exact dollar amount rather than rounding to whole shares. Fractional shares are useful if you have $1,000 and the fund costs $150 per share — you can buy 6.67 shares instead of being forced to buy 6 or 7.

Enter the number of shares and review the order. The brokerage will show you the total cost, including any fees (usually zero for index funds). Click "Confirm" or "Place Order." Your order is now submitted.

What happens after you place your order

If you place your order during market hours (9:30 a.m. to 4 p.m. Eastern time on a weekday when the market is open), your order will execute at the closing price that day. If you place it after hours or on a weekend, it will execute at the closing price the next market day. You will receive a confirmation email with the exact price you paid and the number of shares you own.

Your brokerage account will now show your index fund holdings. The value will change every day the market is open. This is normal. Do not check it every day — index funds are meant to be held for years, and daily price swings are noise, not signals to buy or sell.

If you want to invest more money later, you can transfer it to your brokerage account and buy more shares of the same fund or a different one. Many investors set up automatic monthly transfers and buy more shares on the same day each month, a practice called dollar-cost averaging. This removes the pressure to time the market perfectly.

Common mistakes to avoid when you start

Do not open accounts at multiple brokerages at once. Pick one, fund it, and invest. You can always open another account later if you want to. Multiple accounts make taxes more complicated and make it harder to track your total holdings.

Do not buy individual stocks or sector funds thinking they will outperform the broad market. The whole point of an index fund is that you do not have to pick winners. Stick with a total market index fund or an S&P 500 index fund for your core holdings.

Do not panic and sell when the market drops 10% or 20%. This happens every few years. If you sell during a downturn, you lock in losses and miss the recovery. Index fund investors who stay invested through downturns end up ahead of those who try to time the market.

Do not invest money you will need within five years. Index funds can drop 30% or more in a bad year. If you need the money soon, keep it in a savings account or money market fund instead.

Frequently Asked Questions

Do I need a lot of money to start investing in an index fund?

No. Most brokerages let you start with $1 to $100. Some index funds have minimums of $500 to $3,000, but many brokerages offer the same index funds as ETFs (exchange-traded funds) with no minimum. Fidelity and Charles Schwab are good choices if you want to start small.

What is the difference between a mutual fund and an ETF?

Both are index funds, but they trade differently. Mutual funds trade once per day at the closing price. ETFs trade throughout the day like stocks. For most people starting out, the difference does not matter — pick whichever your brokerage makes easiest to buy. ETFs often have lower expense ratios.

Can I lose all my money in an index fund?

Theoretically yes, but it would require the entire U.S. stock market to go to zero, which would mean the economy has collapsed. In practice, index funds are among the safest investments because they own hundreds or thousands of companies. A single company can fail; the whole market cannot.

How often should I buy more shares after my first investment?

That depends on your income and goals. Many investors buy more shares monthly or quarterly. Some buy once a year. The frequency matters less than consistency — investing $100 every month beats investing $1,200 once a year because you spread out your purchases across different market prices.

What if I make a mistake when placing my order?

If you catch it before the market closes, you can usually cancel the order through your account. If the order has already executed, you can sell the shares when ready and buy the correct fund instead. You will pay a small loss on the price difference, but it is usually small enough to be worth the correction.