For Caroline Li and Colin Wang, moving in together after dating for eight months was a matter of serendipity and urgency.

Last fall, Mr. Wang, 28, was completing his final year of medical school at the University of California, Los Angeles, when he learned that the two-bedroom apartment he shared with one roommate had a mold infestation. He had to move out immediately, but had trouble finding new housing.

“It was very difficult to find something that was pretty close to campus that was reasonable in price, and it was also in the middle of the school year,” said Mr. Wang, who had reached U.C.L.A.’s three-year limit on student housing, which allowed him to pay $1,425 per month in rent instead of the market rate of $2,000 or more.

At the same time, Ms. Li, 24, a registered nurse, learned that one of her two roommates was moving out of their $5,000-a-month, three-bedroom apartment near Santa Monica, Calif., in the middle of their lease. Ms. Li and Mr. Wang realized that they could resolve both of their issues by having Mr. Wang move in with Ms. Li and her roommate.

Ms. Li and the roommate each pay $1,750 per month, and Mr. Wang pays $1,500.

“I think the plan was always for Colin and I to move in once he completed his residency, not once he graduated medical school,” Ms. Li said. “But I guess the opportunity presented itself earlier, and we were able to keep this apartment and save some money while doing it.”

Ms. Li and Mr. Wang are among the many young couples who are choosing to move in together early in their relationships to save money on housing and living costs. Faced with a low inventory of affordable housing, steep competition among buyers and renters, a slow decline in rent prices and climbing mortgage rates, young people across the country are being pushed into finding creative ways to afford housing.

“Younger generations are really having to look for ways to be thrifty and bring their housing costs down, especially in big cities where rents are still really high and home prices are really high,” said Hannah Jones, a senior economic research analyst for Realtor.com.

According to a recent survey from Realtor.com, 80 percent of Gen Z respondents and 76 percent of millennial respondents who have moved in with a romantic partner said finances or logistics, or both, had contributed to their decision.

Ms. Li and Mr. Wang’s apartment is on the top floor of a midrise building, which has a gym. Their apartment has an in-unit laundry and updated appliances, and is close to the beach and major highways. They evenly split the cost of monthly utilities and groceries with their other roommate.

“They actually let me have a bit of a deal when I moved here, because I didn’t have a salary until recently,” said Mr. Wang, who just started his residency program and has more than $200,000 in medical school debt.

Ms. Li and Mr. Wang said that since moving in together, they had improved their communication and had become better at prioritizing quality time together. But they continue to work on merging their living styles.

“Even with roommates, you have to respect each other’s boundaries and whatnot,” Ms. Li said. “But when it’s your partner, I feel like the space you share is so much more intimate.”

While splitting the cost of rent has its benefits, moving in together early on in a relationship can cause issues if a couple don’t already have a good understanding of each other’s communication styles and conflict-resolution skills, said Nicolle Osequeda, a licensed marriage and family therapist in Chicago.

“If there are significant differences and there isn’t a foundation around how we talk about difficult things, be it finances or anything else, then it can exacerbate some of those stresses that you would already feel,” said Ms. Osqeuda, who specializes in working with young adults and young couples through life transitions.

After seven months of dating, Kaitlin Cadagin, 26, and her 28-year-old boyfriend moved into a one-bedroom apartment in a high-rise in downtown Chicago.

Their apartment cost $2,400 a month in rent and offered a number of amenities, including a dog run, a conference room and in-unit laundry. The couple decided to split their rent based on their incomes: Ms. Cadagin, an events manager, paid $1,000 per month, and her boyfriend, a licensed attorney, paid the remaining $1,400.

“I came into it saying, ‘I can afford $1,000 as my portion of the rent,’” said Ms. Cadagin, who was previously renting a two-bedroom apartment with a roommate in another area of Chicago where they each paid $900 per month.

When her roommate decided to move out, Ms. Cadagin said, she and her boyfriend concluded that moving in together would be more cost efficient for Ms. Cadagin than if she rented an apartment on her own. Ms. Cadagin said she could afford to live alone, but preferred to save money by living with someone else.

“I’ve started looking at master’s programs this year, so finances are always on my mind,” she said.

When paying for utilities and groceries, the couple split the cost evenly. Keeping tabs on their shared finances, however, hasn’t always been perfect, Ms. Cadagin said.

“He’s very on top of his finances, and I sometimes am not,” she said.

Ms. Cadagin’s boyfriend, who asked not to be named for privacy reasons, said that although they hadn’t done a good job of setting financial expectations before moving in together, they had learned how to do a better job at setting financial goals together and had become a stronger couple.

Overall, Ms. Cadagin said, moving in with her boyfriend has been a positive experience, and she feels that their relationship still has room to grow.

“I think it’s definitely been a test of our relationship living together, but it’s also strengthened it a lot, and I feel so comfortable with him,” she said.

But not all relationships survive after a newer couple decide to move in together.

In June 2021, Eva Hersch, 26, and her boyfriend moved to Philadelphia together after one year of dating in New York City. In New York, they had lived separately: Ms. Hersch rented a small studio apartment for $2,000 per month, and her boyfriend rented a small one-bedroom apartment for $1,900 a month — a “Covid deal” that would soon be raised to $3,200 per month.

When Ms. Hersch received a job offer in Philadelphia, she persuaded him to move there with her. They chose a two-bedroom apartment for $4,000 per month and split the rent evenly.

“It was just so cheap compared to what we were each paying in New York City,” Hersch said.

Two years later, Ms. Hersch and her boyfriend decided to end their relationship and move out of their apartment, which required them to break their lease.

Ms. Hersch, who now lives in Norwalk, Conn., said moving in with her boyfriend had felt like the “right next thing to do” at the time. They bought a car together and split the monthly payment evenly; they also split the cost of utilities and groceries evenly.

“It was the time when, like, everyone was doing the same thing if they were in a relationship, given most of those people didn’t move out,” said Ms. Hersch, who added that moving in with her boyfriend had taught her a lot about herself and what she wanted in a future relationship. Looking back, she said, she wishes they had waited longer to move in together.

“It was a good thing to try,” Ms. Hersch said. “It’s going to take a lot for me to get into another relationship now.”