For Hazel Findley, moving in with her boyfriend was almost an accident. It started with a series of sleepovers, until the McMinnville, Oregon resident realized that most of her belongings were already at his apartment.

“It was a moment of like, ‘Okay, I’ve slept here more in the last month than I have at my place. What does that mean?’” Findley recalled. “We have a house now, and we’ve been there 11 months.”

Findley’s actions are consistent with a growing trend of millennials who are living together before marriage. The number of cohabitants in the United States rose 29 percent between 2007 and 2016, according to a study from the Pew Research Center. Of the 18 million cohabiting Americans, 50 percent of them are under the age of 35.

Patricia McManus, an associate professor of sociology at Indiana University, has seen this trend within her classrooms. During a 2007 in-class survey of 137 students, 40 percent said they would not consider cohabiting. In 2017, only 13 percent echoed the same thought.

“Most young adults, most millennials, will certainly live together before marriage,” she said, pulling the data from a slew of multi-colored pie charts in her Bloomington, Indiana office. “It’s become more of a norm with less of a stigma.”

McManus’ research outlines a variety of reasons why this trend has gained traction in the last decade. Here, from her files and pie charts, are four things to keep in mind about the cohabitation trend.

It’s Easier On Your Pocketbook

Adults who don’t live with a partner are twice as likely to live below the poverty line, according to the Pew Research Center.

When Paige Craft moved in with her now-husband nine years ago, it was mainly about the money. The quest to make rent cheaper led them to venture out of their parents’ houses and into an apartment closer to their campus.

With their combined incomes, the couple was able to more easily afford not only a place to live, but everything else as well. Even so, the two had to work out some of the kinks of a new financial situation.

“At first, we split things halfway because that seemed like the fair way to do it,” the 27-year-old Craft said. But she made less money than he did, and felt the burden.

“As we grew into our relationship, we made finances work out so it was beneficial and fair to us as a unit, instead of us as individuals,” she said from her home in Council Bluffs, Iowa.

Often, said McManus, cohabiting couples are trying to put money in savings, possibly for a wedding ceremony. “Marriage is in fact an investment in the future,” she said. “Many cohabitants are saving up for that.”

You Get To Know Them Better

Kaleb King of Durant, Oklahoma, admits that his girlfriend Alexandra Kysiak learned a thing or two about him when they moved in together six months ago. For example, he likes his alone time. He also said he’s stubborn, never cleans the water off the sink, and thinks he’s always right.

As for King? He had to learn how to share his food.

“You truly don’t know someone until you’ve lived with them,” said the 26 year old. “You learn all about your partner [when you cohabit] – from the good to the bad.”

Sometimes, taking the leap to get to know each other better can be a frightening stage in a relationship.

Kysiak, 28, and King had only been together a few weeks when her lease ran out on her apartment. Although they had been friends for years, they were still learning to navigate the waters of their newly formed relationship. They decided to move in together anyway.

“I was a little worried that if things didn’t work it would ruin the relationship,” she admits. “But it’s actually been great since the very first day.”

One of her favorite parts about living with him has been discovering the shared activities they enjoy.

“We watch shows together and make fun of them,” she shared. “And he cooks us dinner most nights. I’ve learned he’s a much better cook than me.”

You’ll Fight

King likes his alone time. For him and his girlfriend, figuring out how to get him the space he needed took very little negotiation.

“I’m a pretty upfront guy,” he explained. “So I’ve just told her that I like my time alone. It helps that she doesn’t like football, so when it’s on she goes and watches something else.”

It’s not always so easy.

For some people, the things you learn about your significant other aren’t always things you like. Victoria Fletcher, for example, hates that her boyfriend sleeps with the TV on.

“I like to sleep with total darkness and quiet,” said the 22-year-old resident of Seabrook, Texas. “It affects our sleep and we’ve had to adjust.”

Adjusting to the other person’s preferences, Fletcher said, is the most difficult part of living with them – whether you’re cohabiting or married.

“It’s about trying to acclimate your personal tendencies with the other person’s,” she said.

Kysiak said that living in close quarters makes disagreements harder.

“If we have a fight it’s difficult to get our own space,” said Kysiak. “We don’t fight very much, only two or three times a year, but it’s tough.”

For Findley, the fights are just par for the course.

“You just have to be willing to communicate and put your soul on the table time and again,” she said. “If they can’t give that back to you, it won’t be worth it.”

It Might Not Guarantee A Happy Marriage

According to McManus, there’s no evidence that cohabitation guarantees a happier marriage. This view, while cynical, is one that McManus said has existed in sociology for decades.

“It’s a longstanding research finding that cohabitants have higher rates of divorce,” she said. “And there’s no evidence that cohabitation saves a marriage, either.”

Personal experience doesn’t always support McManus’ theory, and cohabitants like Craft believe this information may be outdated. She said that living together prior to marriage helped make her eventual nuptials more successful.

“People talk about the ‘honeymoon phase’ after marriage, and then things start getting hard,” said Craft. “I think that’s better off being had before the legal commitment to each other.”

Findley, 20, agrees.

“I’m so glad we’ve lived together before,” she said. “Marriage is already a lot of stress, so going through everything we have in living together and trying to be married at the same time may have been the death of me.”

Kysiak suggests having a conversation ahead of time about what cohabitation means to each person in the partnership.

“For some people, cohabitation is a step toward marriage, for others it’s about convenience and saving money,” she said. “Make sure you’re both on the same page about what it means.”

Living Together Before Marriage Is Gaining Traction

McManus said that millennials are becoming more comfortable with the prospect of cohabitation, which is what sparked the trend’s upward motion. The social acceptability of moving in together, she said, has even led to longer periods of cohabitation. But whether it’s better to take the leap and move in with your significant other or wait to tie the knot, she can’t say.

“I can only speak to the trends,” she said. “And the trend is that cohabitation is up. But marriage is still a big deal in America.”

Findley’s cohabitation experience has made her more confident about the prospect of marriage. Even with the ups and downs, she has no regrets about deciding to move in with her boyfriend.

“I know that he’s my person and that marriage is our future,” she said. “But I’m so glad we learned about each other first.”