Working at a start-up that is bought can feel like winning the lottery. Not working at a start-up, but still cashing in on its acquisition, can feel pretty good, too, as Eric Martin learned when Jet.com was sold to Wal-Mart for $3.3 billion.

Martin, who works for a custom bath installation company, received 100,000 Jet shares last year when he won a contest to see who could get the most people to sign up for memberships to the online shopping site. He spent $18,000 on online ads and came away with a stake now worth millions in one of 2015's buzziest start-ups.

"It feels good; it feels really good," Martin, of York, Pa., said in a phone interview.

Martin, 30, has no idea what his stake is worth, though Fusion reported last year that his shares may be valued from $10 million to $20 million. The cash-and-stock sale to Wal-Mart could have boosted that since Jet's private valuation was pegged at around $1.5 billion last November, but the company also has raised money since Martin won his shares.

That could have reduced the value of his stake because start-ups sometimes give preferential shares to later-term investors that can squeeze out smaller investors or employees. Martin is still waiting for Jet to tell him how much his stake is worth, but he's hoping it's in the "multimillions."

Wal-Mart's purchase gives the world's largest retailer a way to boost its online offering and better compete with Amazon.com. Jet's founder, Marc Lore, worked at Amazon for about two years after selling his previous company to the e-commerce behemoth. He founded Jet as a members-only online retailer, aiming to cut prices below even what Amazon could offer.

Martin is thinking about his own start-up, Ideadash.com, an online portal that lets people post ideas for inventions or businesses and get others to execute them while retaining a stake in the project.

"I'm weighing my options," he said. "I've got to take time to process all this."