Paying rent is one of the last—and largest—vestiges of paper-check-writing in the U.S. and it’s also remarkably inefficient. Combine that with the fact that rent is often one of the largest monthly costs for the country’s roughly 100 million tenants and it’s easy to see why Yapstone has focused on rent payments as one of its most critical verticals.

“We want to focus on multi-billion-dollar opportunities,” said Yapstone President David Weiss.

It’s also important to remember that paying that monthly rent bill is only one part of the tenant—and landlord—financial reality. By selling the service to both apartment dwellers and apartment managers, Yapstone has the perfect audience for a group of services that make the rental process easier and therefore more profitable.

“We’re offering a whole range of value-added services such as credit reporting, renters’ insurance that follows that resident from unit to unit,” Weiss said. “This is a powerful series of products that enable us to tap into a $400 billion to $500 billion market.”

Like mobile wallets, the idea is for consumers to get comfortable with the service in one area and then quickly move to use it to pay for everything, far beyond the apartment costs. “That rent check is often half of your wallet,” Weiss said.

Then there are the demographics. It just so happens that a huge percentage of apartment renters are young enough to be in the mobile sweetspot. “Every single person below a certain age does want to pay by check,” Weiss said, adding that that age is likely around 32.

But Yapstone has been very careful to expand to payments-related items—such as damage insurance—while avoiding other rental services. “We have no interest in being in the apartment search business. We don’t want to be a competitor to Zillow or RadPad,” Weiss said. Instead, they want to offer apartment payments services to those kinds of companies. “Most of those marketplaces have no interest in being a payments company.”

Yapstone annually processes transactions worth $16 billion to $17 billion, with revenue just shy of a quarter-billion dollars. With a 45 percent annual growth rate, the company is eyeing rapid expansion. It already operates in 22 countries—including the U.K., France, Italy, Germany, the Netherlands, Portugal, Spain, Belgium, Austria, Switzerland, Luxembourg, Finland, Sweden, Denmark and Canada—with expansion plans next year for Australia, Japan and Southeast Asia.

Canada—with expansion plans next year for Australia, Japan and Southeast Asia.