The CEO of $1.2 billion learning platform Preply says it all started with his online search for an English tutor

Behind the glitz of multimillion-dollar funding rounds that define today’s unicorns are often years of founder sacrifices and barely-there paychecks.

Kirill Bigai, the cofounder and CEO of online education marketplace Preply, paid himself virtually nothing for an entire year while getting his now $1.2 billion business off the ground.

“We agreed to not pay each other salaries, because we didn’t have a lot of capital,” Bigai tells Fortune.

“We wanted to really make it successful.

We had jobs on the side…But the majority of our time was still spent with Preply.” The first year of scaling the language-learning platform was extremely tight.

Bigai was 26 when he created the company with cofounder Dmytro Voloshyn in 2012.

Preply raised a small amount of pre-seed funding in its early days, but within a year it was nearly spent, forcing them to bootstrap the business.

Keeping their costs lean, the founders decided to run their company operations out of their hometown of Kyiv, Ukraine.

Keeping overhead low came at a personal cost: The founders had to work two careers to pay their bills.

In the first year, after its pre-seed funding dried up, the Ukrainian entrepreneurs earned no income from the operation.

They spent 60 hours a week working on their start-up, juggling side-hustles to earn just enough to live.

Bigai worked as an implementation consultant at software company Creatio, with prior engineering experience at Nokia Siemens Networks.

Meanwhile, Voloshyn pursued a PHD in machine learning and AI, also moonlighting as a software developer for AB InBev.

With little to spare, the founders ran a lean operation as they worked to prove the business could survive.