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Last updated on March 4, 2026
Accumulator co-founder Oskar Hartmann explains why angel investing isn’t about complex models or perfect timing; it’s about using your founder perspective as your edge. Here’s his four tips on how to become an angel investor.
Founders often approach investing as a structured, analytical exercise – scanning markets and comparing deals. Yet Oskar Hartmann, co-founder of Accumulator, takes a different view. A serial entrepreneur and global angel investor with 14 unicorns in his portfolio, and recognised among the Top 20 Business Angels in the World by CB Insights, he believes the true edge in angel investing lies elsewhere.
Here’s Oskar’s four strategies on how to start angel investing.
1. The Founder Bubble Is an Asset for Angel Investing
When you start a business, you enter a unique bubble. You work with hundreds of suppliers, partners, and service providers, and a few consistently stand out. I once saw suppliers create entirely new solutions in marketing and logistics that delivered extraordinary value – yet I dismissed them as “just contractors”, not investments.
This is the founder’s advantage: you see execution quality first-hand. Startups collaborate with other ambitious startups. You are surrounded by people building at the frontier. In my first three years, I had over a thousand meetings with entrepreneurs and angel investors – an education in recognising strong people early.
We assume investing must be systematic. In reality, perspective, shaped by operating experience, often matters more than spreadsheets.
2. Startup Peer Networks Outperform Broad Deal Flow
In every company I built, peers were running similar models in other geographies. My first real successes came from backing the same business model I was building, but in different markets. This strategy works because you understand the metrics, risks, and success factors – and can add value from inside the ecosystem.
When I invested in the used-car auction model across 12 countries, six became unicorns. Each market produced its champion. The same pattern is visible today in sectors like neobanking: founders invest abroad in models they deeply understand. This is why angel investing is often about aligning with ecosystems that you know, rather than making individual stock picks.
3. Communities Beat Selection Skill
Ecosystems matter more than individual brilliance. Through my university alumni network, I became an early angel investor in around 10% of German unicorns. In India, four of my seven investments became unicorns – not because of superior stock-picking, but because I was early inside the right community.
My most painful insight: cherry-picking reduced returns. Had I backed everything emerging from that strong bubble, I would have done better. I was better at identifying high-quality environments than predicting individual winners.
That insight led me to build an Accumulator platform. It is a way to index a trusted founder bubble through community.
Most founders have the same problem: nearly all their wealth sits in one company. Accumulator reduces that concentration, shifting founders from ~95% to ~85% in their own startup and increasing diversified exposure from ~5% to ~15% – a ~3× improvement – without selling or sacrificing upside.
That exposure is spread across category-leading private tech companies from the same high-quality founder network. For founders too busy to do disciplined angel investing at scale, this is a rational way to reduce risk and become an investor in more success stories at the same time.
Shared ownership then becomes the binding layer. When founders and angels with real outcomes have vested interest in each other’s success, you get a peer community where advice is practical and incentives are aligned.
4. Where Founders Should – and Shouldn’t – Angel Invest
Avoid conflicts of interest. Investing where you control budgets or insider information is poor governance and problematic with external investors. I learned this the hard way and had to unwind an investment under board pressure.
A healthier source of deal flow is former employees who leave to build companies. Many successful ecosystems, including Airbnb’s, produced dozens of founders this way. I have invested in departing team members many times – and never regretted it.
Finally, manage concentration risk. Founders are already exposed to one sector. Keeping at least 50% of capital in low-risk assets – ETFs, index funds, or property – enables smarter venture risk-taking elsewhere.
Large conferences are overrated. Everyday proximity reveals hidden champions.
In the end, investing remains a people business – and founders already sit closer to the opportunity than they think.
Click here to learn more about Accumulator.
