What could be worse than handing out 50% of your company's equity to a co-founder who doesn't understand the product as much as you do, and all they seem to bring is the ability to talk?

Likewise, a sales-focused founder may be struggling to know what makes you great, or - worse - may not appreciate the importance of development.

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At PostHog, Tim didn't even know he wanted to start a company, so the answer here was yes!

For introverts, your inclination might be to retain complete control and to hire someone to handle the business side of things. This leads itself to a standard failure mode - not talking to users. You'll find it easy to build, but you'll have a hard time building something people want.

With a true co-founder, you can bounce major decisions off a sounding board before going live. At PostHog, James is responsible for bringing in new customers (among his other CEO duties), while Tim is responsible for overseeing engineering as CTO. They both hold each other accountable, ensuring that any off-course outcomes are corrected swiftly.

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Longer term, running a company is stressful - you're creating something out of nothing, and that inherently means you'll question yourself. Perhaps the most basic thing that has worked well at PostHog is James and Tim have managed to continuously rationalize what we're doing - taking it one problem at a time. We pivoted five times in the early days, and we'd not be here today without two people pushing each other to get over each hurdle.

As a salesperson, watching a developer feels like magic. A whirr of terminal windows then suddenly a product makes its way into real life. Likewise, to a developer, the instant relationship-building skill a good salesperson has is critical to getting a product off the ground.

Don't get sold too soon - relationship-building for a salesy cofounder is table stakes. In addition to these respective skills, you'll also need this person to have:

• The ability to get stuff done
• A product-focused mentality
• The ability to adapt

And, crucially, you need to like working with each other.

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If you're comfortable talking with strangers that often do not want to talk to you, then two developers is probably the best possible setup. One of the things that was noticeable during PostHog's time at Y Combinator was how outgoing many of the technical founders were.

It has been very important that James can do the basics of development. Optimally, both would be kick-ass developers, but that has been less important than selling and communication skills with external parties - users, customers, employees, and investors.

Cofounder breakup is a key way for your startup to fail.

There are a few things PostHog did to guard against this:

• Equal equity between cofounders - even if you didn't start on the same day. This can otherwise cause resentment.
• A culture of direct feedback. James and Tim tell each other when they get frustrated and have encouraged the team to do this too.
• Clear individual goals for each week. There was a ton of stuff to build in the early days, so James' job was everything else: getting user meetings, making wireframes, working out how to do taxes and payroll, raising money, or buying food. He even did some paid consultancy to make some money to pay for ads early on. Meanwhile, Tim focused on coding. This is how we got so far so quickly.
• Both cofounders are involved in key decisions. To stereotype - salesy types tend to be more extroverted and can dominate the direction of a company. James and Tim, even with a team of 20, double up their one-on-ones to 2 hours each week to stay close and remain aligned on key decisions.
• Work out what you both want out of life. Are you trying to retire early or is it the pure challenge? Go deep to figure out what the company and startup journey means to each of you.

Having a co-founder is great - but it's far better to have no co-founder than to have the wrong one. Getting this right is perhaps the most crucial decision you'll take on your road to startup success.