From left: Gabe Lehman, Elana Maslow, Aviva Maslow with Aurora, and Noah Orgish in Berkeley, Calif. The two couples put their funds together to buy a multifamily home. Jason Henry for The New York Times

For years, Aviva Maslow and her younger sister Elana casually joked about buying a home together. The two had grown up in a tight-knit family in Marin County, north of San Francisco, before going their separate ways for college and early careers. By the time Aviva, 34, and Elana, 32, circled back to the area around the COVID-19 pandemic, the difficulties of buying a home were setting in.