I bought a duplex with my sister in San Francisco. We share resources, split the mortgage, and babysit for each other.

After college and stints abroad, my younger sister and I rented a two-bedroom apartment in San Francisco. Our living situation was glorious. We decorated our place with a mix of old and new, we binged our favorite shows, and we hosted New Year's Eve. More than once, people told us, "You can't live with your sister forever." But it turns out you can.

Fast forward a few years and add a husband, a kid, and a dog each, and we're still living under the same roof — sort of. Our two families bought a duplex together near Golden Gate Park. She lives upstairs. We live downstairs.

What started as a practical decision — splitting the cost of homeownership in an expensive city — turned into something so much more. Sure, there's a lot of chaos. My nephew eats all our snacks, and my dog keeps breaking their screen door, but life is more fun — and affordable — than I could have ever imagined.

Buying a duplex together was a smart financial move

We love our city, but San Francisco is expensive. Splitting the mortgage, property tax, and insurance made it feasible for us. And every month, we continue to save on utilities, like garbage and water. We also save on surprise costs that pop up, such as front stoop repairs and a roof leak that affected both homes.

Both families benefit from living in the same duplex. Courtesy of Nicole Findlay

We have built-in babysitting

One of the best perks of sharing a duplex is that not only do our two little guys get to grow up together, but there's also a reliable babysitter just a flight of stairs away. We schedule monthly date nights, so every few weeks, my husband and I get a night out on the town, and vice versa. The cousins love it. For them, it typically means pizza, popcorn, and sleeping bags on the living room floor.

But what's even more valuable than scheduled babysitting is the last-minute saves. If my sister and brother-in-law both have morning meetings, I'm around to drop off my nephew at school. If we need coverage, they watch my little one. And it's not just the kids that benefit. Sometimes, when we get home after a long day out, our dog is waiting for us — cuddled on the couch with her upstairs family.

They share resources and babysit for each other. Courtesy of Nicole Findlay

We share resources

Living downstairs from my sister brings the neighborly "Can I borrow a cup of sugar" to the next level. If I need a splash of milk for my morning coffee, a slice of bread for my son's lunch, or a can of beans for dinner, I can pop upstairs to see if I can "shop" it there before running to the store.

If my sister gets a box of donuts, she calls us. If I make muffins, I'll knock on her door. My favorite surprise, though, is the random evening text: "I just opened a bottle of wine."

My closet is twice as big

I have twice as many options when looking for something to wear. It might sound silly, but I haven't shopped (hardly) at all since moving downstairs from my sister. We wear the same size clothes, and her closet is better than most boutique shops. I'm the clear beneficiary in this situation, but I make up for it in other ways, like always having snacks in the pantry.

Our unique living situation may not last forever, but for now, it makes life a little bit more affordable and a lot more fun.