For most of my life the script was fixed: you grow up, you move out, and success means never moving back. The numbers now say America is quietly rewriting that script, and the housing type I live in, a duplex, happens to be the best-designed answer to the problem the rewrite creates.
The reversal, in three numbers
In 1971, 7% of Americans lived in a household with two or more adult generations. By 2021 it was 18%, nearly one in five people, according to Pew Research Center.
The buying side moved even faster: the National Association of Realtors (NAR) reports that multigenerational purchases reached 17% of all home purchases in 2024, an all-time high. And the reason has flipped from preference to arithmetic. In 2015, 15% of multigenerational buyers named cost savings as their motivation; by 2024 it was 36%, the most common answer.
Nothing mysterious is driving this. Young adults face entry prices their wages did not keep up with, older parents are living longer and need help, and childcare costs rival a mortgage payment. Three problems, one roof.
The hard part is not money, it is proximity
Every family that has tried the one-big-house version knows the failure mode: everyone loves each other slightly less at zero feet of distance. The arrangements that last are the ones that create closeness without constant togetherness, and that is a floor plan question. Separate entrances. Separate kitchens. A door that closes and a threshold nobody crosses uninvited.
Which is a precise description of a duplex. A 2-4 unit building is two to four private homes that happen to share a structure, a lot, and a mortgage.
Why a duplex fits a multigenerational household
Grandparents in one unit and the young family in the other is the multigenerational setup with a pressure valve built in: childcare is thirty feet away, so is eldercare, and so is a fully private retreat when the day is done. My own building works this way with a tenant instead of a relative, and the mechanics are identical, which is why I wrote up whether you can house hack with a family separately.
What down payment assistance allows on a 2 to 4 unit home
What Indiana’s housing agency confirmed in writing
Here is the detail I have not seen written anywhere else. While surveying down payment assistance rules for 2-4 unit buildings across 83 metro areas, I asked state housing agencies directly, and Indiana’s agency confirmed in writing that its assistance programs allow buying a 1-4 unit home, with one condition: the extra units may not be rented for profit for the life of the loan. They may, in the agency’s own words, be used for multigenerational housing and family purposes. In other words, at least one state’s down payment assistance is effectively purpose-built for the grandparents-downstairs arrangement, even though it bars the landlord version. State rules differ sharply, and I keep the per-metro details, with sources, on the down payment assistance survey page.
What to look for if this is your plan
- Truly separate entrances, not a shared hallway with two doors.
- Separate utility meters, so nobody argues about the electric bill in July.
- A ground-floor unit that works without stairs, for the parent who is fine today and less fine in ten years.
- Sound separation at the shared wall or floor, the cheapest peace treaty in housing.
- A layout that converts: the family unit of today may be the rental unit of a decade from now, and the mortgage math should work either way.
That last point is the quiet advantage of buying a 2-4 unit building instead of one big house with a finished basement. When the family chapter ends, a duplex becomes an income property with no renovation. A five-bedroom house becomes a five-bedroom house.
If the building in front of you is a single-family house rather than a duplex, there is a second route. Federal law now allows a much higher loan for converting a house into a two-family building, and it added a separate loan category for accessory dwelling units that HUD has not put a dollar amount on yet. I walked through which of those routes are open today.
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Sources
- The demographics of multigenerational households, Pew Research Center (March 2022)
- 2024 Profile of Home Buyers and Sellers highlights, National Association of Realtors (November 2024)
- How families and the data are shaping multigenerational living, National Association of Realtors (May 2025)
Where my figures come from: The Indiana assistance detail is from the Indiana Housing and Community Development Authority’s written reply to my survey question, August 2026. Figures above are as of their publication dates; check the linked sources for updates.
What counts as a multigenerational household?
Pew Research defines it as a household with two or more adult generations, or grandparents living with grandchildren under 25. The share of Americans living this way has grown from about 7% in 1971 to around 18% in recent surveys.
Can you use down payment assistance for a multigenerational home?
It varies by state program. Indiana’s agency confirmed to me in writing that housing family members in the other unit is allowed while renting to strangers is not, under their assistance program. Always ask the agency directly before you count on it, because the answer changes state by state.
Is a duplex good for multigenerational living?
It is one of the best fits. Separate entrances, separate kitchens, and a shared building mean everyone keeps their own space while staying close. You get the closeness without the constant togetherness that wears families down in a single shared house.
What is multigenerational living?
Multigenerational living is defined as a household containing two or more adult generations, such as grown children living with parents or parents living with grandparents, sharing one property.