Looking to invest more in their friendships, some are opening shared bank accounts

A novel way to maintain strong friendships?

A novel way to maintain strong friendships? Creating a joint bank account.

That's the advice Madison Machen received last year while chatting with her seat-mate on a flight to New York. The woman was on her way to meet her best friend on one of their periodic trips. The trip, she told Machen, was funded by her joint account with the friend.

"I loved the concept so much, I went home and I called my best friend and I was like, I think we need to do this," Machen said.

Six months later, the Austin, Texas, resident and her friend Kim had saved over $1,000 in their joint Cash App account. Next up: A trip celebrating their 20th friendship anniversary next May, Machen said, hopefully in the south of France.

"It’s fun for us, because we can do little wagers, almost like a swear jar," Machen said. "I’m training for a marathon right now, and one of my goals was, if I skip my long run, or if I skip any of my runs, I have to put in $5."