The #1 killer of startups isn’t fundraising

One of the hardest lessons I have learned in building companies has nothing to do with fundraising, product, or sales. It is about co-founder dynamics.

Startups are unpredictable. People’s lives change. Visions drift. Sometimes the sheer intensity of building becomes too much. And yet, those moments do not have to mean the end of a business. In one of my own experiences, a co-founder breakup actually accelerated growth. I will share that story in a future post.

I will be honest. I have been through it and it is horrible for both parties. Believe me, you do not want to get into that spot. Ego gets involved, and ego is almost always the killer of the business. You have to fight for the mindset that the business comes first. The goal is for the company to continue, not for you to win the argument.

This is not only my perspective. A 2022 study found that 65 percent of startup failures are linked to co-founder conflict. Paul Graham from Y Combinator once said, “Most of the problems startups face are internal. The number one internal problem is co-founders.”

We have all seen the high-profile examples:

• Twitter went through painful co-founder splits but kept growing.
  

• Facebook had a messy breakup between Mark Zuckerberg and Eduardo Saverin, yet scaled to billions.
  

• Even Apple. Steve Jobs left after conflict, only to return and lead its biggest growth era.

The point is clear. A breakup does not equal death. If managed properly, it can reshape a company for the better.

Lessons Learned Along the Way

Building alongside my current co-founder Razvan, who has been with me through the stages of VAUNT, I have collected some lessons that matter most.

1. Alignment is everything
At the beginning, everything feels exciting. Growth and pressure will test that alignment. If your visions do not match, cracks show up fast.

2. Define roles clearly
In the early days, everyone does everything. Without defined responsibilities, conflict slips in quietly. Clear structure removes friction.

3. Be honest about intensity
Startups demand resilience, speed, and sacrifice. It is not for everyone. Having that conversation upfront prevents resentment later.

4. Build resilience into the company
A startup should not collapse if one person leaves. Processes, culture, and knowledge-sharing matter just as much as product.

Early Warning Signs

Before you commit, test-drive the partnership. Work together for a period of time on real problems. You will quickly see if you share values, pace, and decision-making style.

Conflict Resolution Playbook

When conflict does show up, we try to talk like adults. Sometimes that means saying:
“This is not a productive conversation. It makes me resentful. Let’s take a step back and talk later.”

It sounds simple, but pausing prevents the ego from taking control. Most conflicts boil down to ego. Both sides feel entitled and convinced they are right.

The Emotional Side

A co-founder breakup feels heavy because it is not just business. It is trust, friendship, and identity wrapped together. The truth I learned is this: a real business has to survive with or without its founders. That is when you know you have built something with legacy.

A Practical Exercise from a Mentor

A mentor once taught me this exercise. The next time you fly somewhere with your co-founder, use the long flight as a check-in. Each of you separately writes down:

• When you think the business should pivot
  

• What is the ultimate goal
  

• What outcome you want personally and professionally

Then compare notes. Misalignments show up quickly. You can address them before they become cracks.

Write Everything Down

Even if you are best friends or best partners, put things in writing. A founder agreement, rules of conduct, vesting terms, and documented responsibilities are not about mistrust. They are about protecting the business.

Structure keeps everyone in check. When emotions run high, it is the framework that saves the business.

How We Built VAUNT Stronger

At VAUNT we have applied these lessons:

• We have a code of conduct and clearly defined roles.
  

• We hold regular check-ins and accountability sessions.
  

• We created a playbook for adding future executives or even another co-founder, with responsibilities documented before they join.
  

• Most importantly, we built the company with the belief that VAUNT must outlast any individual founder.

Advice for Founders

• Treat co-founders like life partners. Values and vision matter more than enthusiasm.
  

• Write everything down. Goals, equity, roles, responsibilities, and rules of conduct.
  

• Check in regularly. Not just about business but also about life.
  

• Check your ego. You have to want the business to survive more than you want to be right.
  

• Use structured exercises. Flights, off-sites, or even a quiet afternoon can help reset alignment.
  

• Accept unpredictability. Success is not about avoiding conflict but navigating it without losing momentum.

I would not trade these experiences. Even the painful ones shaped how I build today. And I am grateful to have a co-founder who has been through those building stages with me and with whom I share trust and alignment.

The truth is simple. Startups are built on trust, clarity, and adaptability. Not only on product and capital.

A few words about me

I’m Irina Constantin—entrepreneur, educator, and avid reader with over a decade of experience in the tech industry. I’m the CEO and co-founder of VAUNT, a bootstrapped, profitable pro-tech startup transforming how residential developers sell properties worldwide.

I started my entrepreneurial journey at 21, founding a software development agency focused on B2B and B2C products. Today, I’m building VAUNT into the operating system of the residential industry. Over 80 developers actively use our platform to manage more than $2 billion worth of properties.

I’m passionate about leveraging technology to solve real estate challenges and committed to building solutions that create lasting impact. My work has earned me recognition, including being named to the Forbes 30 Under 30 list in 2022.

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