(|Best Side Hustles: Your Guide to the Ultimate Passive Side Hustles and Financial Growth)
Introduction: Why Your Phone is Your Best Wealth Tool
If you’re looking for the best side hustles in Spain, the answer isn’t another job; it’s smart investing. In 2025, the complexity of the stock market has been replaced by a few powerful, easy-to-use mobile apps.
For beginners in Spain, choosing the right platform is critical. You need low-cost EU regulation compliance and automated investment plans that fit your busy schedule. This guide breaks down the absolute best, most secure apps tailored for the Spanish market, allowing you to turn a small monthly contribution into long-term financial stability.
Stop trading your time for money. Start using these apps to build an asset that works for you.
The Champions – Best All-Around Apps for Beginners
These apps are perfect entry points. They offer simple interfaces, low costs, and comply with EU regulations (crucial for tax declarations to the Hacienda).
1. Trade Republic (The Commission-Free Powerhouse)
Trade Republic remains the gold standard for beginners in Spain, combining the accessibility of a mobile app with the low costs needed for frequent investing.
- Best For: Automated Monthly Investments (DCA) and Quick Mobile Trading.
- The Killer Feature: Free, automated savings plans (DCA). You can set up automatic monthly investments into popular ETFs or fractional shares with zero transaction fees. This is the ultimate “set it and forget it” side hustle strategy.
- Cost: Generally commission-free trading.
- The Spanish Advantage: Fully licensed as a bank in Germany and operates under EU regulation, simplifying tax reporting compared to non-EU brokers.
2. DEGIRO (The Low-Cost European Veteran)
DEGIRO is an essential platform once you move past the absolute beginner phase and start building a larger, more complex portfolio.
- Best For: Serious investors building diversified portfolios of ETFs and international stocks.
- The Killer Feature: Vast selection of commission-free ETFs. They offer a comprehensive list of popular ETFs (like those tracking the MSCI World or S&P 500) that you can buy and sell without transaction fees.
- Cost: Extremely low commissions on non-free products, making it one of the most cost-effective brokers in Europe.
- The Spanish Advantage: Excellent range of markets (Madrid Stock Exchange included) and robust reporting tools for Spanish taxes.
Niche and Advanced Earning Tools
Once you have your core portfolio set up (using Trade Republic or DEGIRO), these apps provide flexible ways to earn extra money through specialized or automated strategies.
3. eToro (The Social Investor’s Choice)
eToro pioneered social trading, making it unique for beginners who lack confidence in their own stock-picking abilities.
- Best For: Copy Trading and learning from established investors.
- The Killer Feature: CopyTrader. You can automatically mirror the trades of successful, proven investors on the platform. This lets you potentially generate returns with minimal effort – a true passive income stream – while you learn by observing.
- Cost: Commission-free stock and ETF trading, but there are fees for crypto trading and currency conversion fees.
- The Passive Angle: It transforms the high-effort task of active trading into a low-effort system, positioning it as an excellent side hustle for busy professionals.
4. XTB (The Analytical Trader)
XTB is a strong option for those who eventually want to move into more active trading strategies like CFD or Forex, but it also offers fee-free stock/ETF investing.
- Best For: Active traders and those wanting professional analysis tools.
- The Killer Feature: Zero-commission stocks and ETFs up to €100,000 monthly turnover. This makes it highly flexible for the dedicated beginner.
- The Skill Connection: Using XTB helps you pick up trending online skills to learn like technical analysis and risk management, which are highly valuable in any market.
5. Binance / Kraken (The Crypto Gateway)
While higher risk, crypto is now a standard diversification tool. Binance and Kraken are the largest and most reputable platforms for buying and holding Bitcoin, Ethereum, and other assets.
- Best For: Building a small, strategic allocation of digital assets.
- The Passive Angle: Both platforms offer staking and interest-earning programs, which are true forms of “make passive income with zero investment“ (beyond the initial capital).
- Crucial Note: Treat this as high-risk allocation (no more than 5-10% of your total portfolio).
The Blueprint – Turning Investing into a Side Hustle
The problem with most articles is they just list the apps. The secret to success is using the apps correctly to achieve genuine financial stability.
6. The DCA System (Your Best Side Hustle)
The single best side hustle for generating wealth is Dollar-Cost Averaging (DCA). It requires almost no time or skill.
- What it is: Investing a fixed amount (e.g., €150) into the same diversified asset (e.g., MSCI World ETF) every month, regardless of the price.
- Why it works: It removes emotional panic and automatically buys more shares when the market is low.
- Action Plan: Use Trade Republic’s free savings plan feature to automate this entire process. You set it up once, and your wealth grows passively.
7. Skills to Learn for Maximizing Returns (The Growth Engine)
While investing is passive, learning the right underlying skills will maximize your results. These are the trending online skills to learn that boost your financial literacy:
| Skill to Master | Why It Matters | Application on Investing Apps |
| Financial Literacy (Budgeting) | Knowing how much you can consistently invest without jeopardizing daily life. | Setting the correct monthly DCA amount. |
| Long-Term Thinking | Avoiding panic selling during market dips (the #1 mistake of beginners). | Holding your DEGIRO/Trade Republic assets for 5+ years. |
| Risk Management | Knowing how to diversify (not putting everything in crypto or one stock). | Creating a balanced portfolio across different asset classes. |
8. Addressing Spanish Taxes (Hacienda)
For Spanish residents, ease of tax reporting is a major factor when choosing an app.
- Capital Gains: Any profits realized from selling assets (stocks, ETFs, or crypto) are taxed as savings income (starting at 19%).
- The Broker Advantage: Many EU-regulated brokers simplify this by providing annual tax reports summarizing your gains and losses, which is invaluable when filing your Declaración de la Renta. Using non-EU apps complicates this.
Conclusion: Your €100/Month Habit
The best investment app is the one you actually use consistently. For beginners in Spain, start with Trade Republic to set up a simple, automated DCA plan into a broad ETF.
Your primary focus should be on building the habit of investing a small amount every month. This simple, automated habit is the ultimate passive side hustle – a low-effort, high-impact action that ensures you are building financial stability every day, without taking a single hour away from your job or social life. Start with €50 today.