There are roughly 45 million unpaid eldercare providers in the United States, according to the 2016 U.S. Census Bureau. It’s tough on these family caregivers, many of whom are working women who are also raising their own children. There are alternatives. For example, there’s no shortage of agencies willing to place a rotating cast of caregivers into the homes of the elderly, though they can be prohibitively expensive for many families. There are also upstarts trying to address the challenge — and opportunity — that an aging American population presents. Now, another startup in the space, three-year-old, San Francisco-based Kindly Care, is taking more of a marketplace approach, pairing vetted caregivers with families who need them, then helping both sides manage their financial and tax arrangements by acting as their back-office provider.