Published: August 31, 2026

If you’ve heard that index funds are one of the best investments for beginners — you heard right. Warren Buffett has recommended them. Most financial experts agree they outperform actively managed funds over time. And in 2026, they’re easier to invest in than ever.

This guide walks you through exactly how to invest in index funds as a complete beginner, including which ones to consider, where to buy them, and how to get started with very little money.

What Is an Index Fund?

An index fund is a type of investment that tracks a market index — like the S&P 500, which includes the 500 largest companies in the US.

Instead of trying to pick winning stocks yourself, you’re buying a tiny slice of hundreds (or thousands) of companies all at once. When those companies grow over time, so does your investment.

Why this matters for beginners:

• Instant diversification — you’re not betting everything on one or two companies
• Low cost — index funds charge very low fees (some as low as 0%)
• Proven track record — the S&P 500 has averaged roughly 10% annual returns historically
• Simple — no need to follow individual stocks or make complex decisions

The main alternative is actively managed funds, where a professional portfolio manager picks stocks trying to “beat the market.” The problem: most actively managed funds underperform index funds over 10+ year periods, while charging much higher fees. Index funds typically win in the long run.

Types of Index Funds to Know

S&P 500 Index Funds

These track the 500 largest US companies — Apple, Microsoft, Amazon, and so on. This is where most beginners start because it gives you broad exposure to the US economy. Popular options include VOO (Vanguard S&P 500 ETF, 0.03% expense ratio), SPY (SPDR S&P 500 ETF, 0.09%), and IVV (iShares Core S&P 500 ETF, 0.03%).

Total Market Index Funds

Instead of just the top 500 companies, these track the entire US stock market — including smaller and mid-size companies too. Great for even broader diversification. VTI (Vanguard Total Stock Market ETF, 0.03%) and FZROX (Fidelity ZERO Total Market Index Fund, 0.00%) are standouts here.

International Index Funds

These track stocks in other countries, adding global diversification. Often recommended as a smaller portion of a portfolio alongside a US index fund. VXUS (Vanguard Total International Stock ETF, 0.07%) is a popular choice.

Bond Index Funds

Bonds are generally less risky than stocks. Bond index funds are often added to portfolios as you get closer to retirement, to reduce volatility. BND (Vanguard Total Bond Market ETF, 0.03%) is the standard choice.

For most beginners just starting out, starting with one S&P 500 or Total Market index fund is completely fine. You can add international exposure and bonds later as your portfolio grows.

Not sure which specific fund to pick? We’ve reviewed the 7 best index funds for beginners in detail — with expense ratios and where to buy each one: Best Index Funds for Beginners (2026) →

How to Buy Index Funds: Step by Step

Step 1: Open a Brokerage Account

You need an account to buy index funds. You have two main choices:

Option A: Robo-advisor — a platform like Betterment automatically builds and manages a diversified portfolio of index funds for you, rebalancing automatically and optimizing for your goals. Perfect if you want truly hands-off investing.

→ Open a Betterment account and get started automatically: [AFFILIATE LINK – Betterment]

Option B: Self-directed brokerage — platforms like Robinhood let you choose and buy your own ETFs commission-free. You pick VOO, VTI, or whatever you want, and buy shares directly. Good if you want to be more hands-on.

→ Start investing commission-free on Robinhood: [AFFILIATE LINK – Robinhood]

Step 2: Choose an Account Type

Inside your brokerage, you’ll choose what kind of account to open. A Roth IRA is best for retirement savings — tax-free growth, max $7,500/year in 2026. A taxable brokerage account has no contribution limits and no tax advantages, but is completely flexible for goals other than retirement.

For most young beginners, start with a Roth IRA if you have earned income. The tax-free growth is one of the best long-term advantages available.

Step 3: Fund Your Account

Link your bank account and transfer money in. You don’t need thousands of dollars — Robinhood lets you buy fractional shares of ETFs starting at $1. Set up automatic recurring transfers so a set amount moves from your bank into your investment account every week or month. This is called dollar-cost averaging, and it’s one of the most effective strategies for beginners.

Step 4: Buy the Index Fund

On a self-directed platform like Robinhood, search for the ticker symbol (like “VOO” or “VTI”), choose how many shares or dollars you want to invest, and click buy. On a robo-advisor like Betterment, you don’t even do this step — they build the portfolio for you.

Step 5: Leave It Alone

This is the hardest step for most people, but it’s the most important one. Don’t check your portfolio every day. Don’t panic-sell when the market drops. Index funds are a long-term strategy. The market goes up and down, but historically it trends upward over 10+ year periods.

How Much Should You Invest in Index Funds?

There’s no single right answer, but here are some practical starting points:

• $25/month: Gets you in the game and builds the habit. Roughly $300/year invested.
• $100/month: Starts to feel meaningful after a few years of compounding.
• $200–$500/month: Gets you toward maxing out a Roth IRA over time.

The most important thing is consistency, not the amount. Investing $50/month for 20 years beats investing $500/month for 3 years every time.

Common Index Fund Mistakes Beginners Make

Waiting to “understand the market” first. You don’t need to understand the market to invest in an index fund. The fund tracks the market for you. Start now and learn as you go.

Trying to time the market. “I’ll wait until prices drop.” The problem: no one can consistently predict when the market will drop or rise. Time in the market beats timing the market.

Picking too many funds. You don’t need 15 different index funds. For most beginners, one or two is plenty. Start simple and add complexity later if you want.

Ignoring expense ratios. Look for funds with expense ratios under 0.10%. Even a seemingly small difference (like 0.03% vs. 1.00%) adds up to tens of thousands of dollars over a 30-year investing period.

The Bottom Line on Index Fund Investing

Index funds are one of the most beginner-friendly, proven wealth-building tools available. You don’t need to be a stock-picking expert, follow market news every day, or have a lot of money to start.

You just need to open an account, pick a low-cost fund, and invest consistently over time.

The best day to start was yesterday. The second-best day is today.

Want to start investing in index funds without having to pick anything yourself? Betterment builds you a diversified index fund portfolio automatically — no experience needed.

→ Get started with Betterment: [AFFILIATE LINK – Betterment]

Or if you want to pick your own ETFs commission-free:

→ Start investing on Robinhood: [AFFILIATE LINK – Robinhood]