A multigenerational home is a property built or set up so two or more adult generations can live together, each with some privacy. In Orange County, the most practical version is usually a house with an ADU or a junior ADU: parents in one unit, adult kids or grandparents in the other, separate kitchens and front doors on one lot. Done right, it’s also one of the safest real estate investments a family can make, because the second unit can be rented when the family no longer needs it.
Here’s what to look for, how the options compare, what it costs, and how families are financing it in Orange County and LA County.
Why Multigenerational Homes Are Growing
About 18% of Americans, or 59.7 million people, lived in multigenerational households in 2021, up from 7% in 1971, according to Pew Research Center. Among home buyers, 14% bought a multigenerational home in NAR’s 2025 Profile of Home Buyers and Sellers. The top reasons:
- Caring for aging parents (41%)
- Cost savings (29%)
- Adult children moving back home (27%)
In Southern California, the cost reason is even stronger. A family pooling incomes can often buy one $1.2 million house with an ADU when neither household could buy alone.
Four Ways to Set Up a Multigenerational Home
| Setup | Privacy | Typical added cost | Rentable later? |
|---|---|---|---|
| Downstairs bedroom suite (no kitchen) | Low | $0–$50K | No |
| Junior ADU (up to 500 sq ft inside the house) | Medium | $60K–$120K | Yes, with its own bathroom |
| Attached ADU or garage conversion | Medium–high | $100K–$250K | Yes |
| Detached ADU (800–1,200 sq ft) | High | $250K–$350K | Yes, highest rent |
Builders also sell “home-within-a-home” floor plans in some newer OC communities, such as Lennar’s NextGen designs. Those work well for family living, but in an HOA tract they often can’t be rented separately the way a permitted ADU can. If future rental income matters, a legal ADU or JADU gives you more options.
I compare the in-house options in In-Law Suite vs JADU vs Detached ADU.
What to Look For in a Multigenerational Home
For aging parents
- Single-level living with no stairs to the bedroom and bath.
- A walk-in shower, wider doorways and room for grab bars.
- A short, flat path from parking to the front door.
- Distance, but not too much. Close enough to check in, far enough for privacy.
For adult children
- Their own entrance and, ideally, their own kitchen.
- Sound separation from the main house.
- A parking spot that doesn’t block the driveway.
For the property itself
- Permits. A “granny flat” in the listing is only an asset if it’s legal. If it isn’t, read buying a house with an unpermitted ADU in Orange County before you write an offer.
- Lot depth and access if you plan to build later. Corner lots and alley access make construction easier.
- Utility capacity. Older homes may need a panel upgrade to support a second kitchen.
If the right house doesn’t exist, buy the right lot. My guide on buying a lot to build an ADU for aging parents walks through that path.
What California Law Allows
State ADU law makes a multigenerational setup easier than most buyers expect. On most single-family lots, you can combine an ADU inside or converted from existing space, a new detached ADU and a junior ADU, per the HCD ADU rules.
- No owner-occupancy requirement for an ADU.
- JADUs with their own bathroom also have no owner-occupancy requirement starting in 2026 under AB 1154.
- Starting January 1, 2027, AB 956 allows two detached ADUs on a single-family lot, which can mean a unit for grandparents and a unit for adult kids.
For the junior ADU size rules, see California Junior ADU Size: The 500-Square-Foot Rule.
The Numbers: A $1.2M Orange County Example
Say two households pool funds to buy a $1.2 million Orange County home with a permitted 2-bed detached ADU. The main house is owner-occupied, so it qualifies for primary-residence financing.
| Scenario | Monthly |
|---|---|
| Total payment (PITI, 20% down, example) | $7,600 |
| Family in ADU contributes | $2,000 |
| Main household’s share | $5,600 |
| Later: ADU rented to a tenant at market | $2,800 |
| Main household’s share after renting the ADU | $4,800 |
The payment figure is an illustration. Use your own rate, taxes and insurance. Once the family member moves out, the ADU becomes income. Some lenders can also count ADU rent toward qualifying. I explain the rules in Using ADU Rental Income to Qualify for Your Mortgage.
Financing and Title Tips for Families
- Decide how title is held before you open escrow. Joint tenancy, tenancy in common and a family trust each have different tax and estate effects. Talk to an attorney or CPA.
- Parents can help without co-owning. Gift funds, co-signing and down payment structures are covered in the smartest way parents can help their kids buy.
- Plan for the inheritance. Prop 19 changed how a parent’s property tax base passes to children. See how Prop 19 affects an inherited property with an ADU.
- Garage conversions can make it affordable. One family used a parent’s gift and a garage conversion to make a $1.1M home work. Here’s the Huntington Beach example.
Where to Find Multigenerational Homes in Orange County
Older central OC cities have the lots that make this work: 6,000- to 8,000-square-foot parcels from the 1950s and ’60s with room behind the house. Garden Grove, Anaheim, Westminster, Fullerton and Orange are where I find the most. In LA County, Lakewood and Long Beach have similar lot patterns.
Many of these homes already have a permitted ADU. Others have an unpermitted garage unit you can legalize under AB 2533. For a city comparison, see the best cities to buy a home and add an ADU in 2026.
Frequently Asked Questions
What is a multigenerational home?
A home designed for two or more adult generations to live together, usually with a separate suite, junior ADU or ADU that has its own entrance and kitchen.
Is a house with an ADU a good multigenerational home?
Yes. It gives each household privacy, and the ADU can be rented later when the family no longer needs it.
How much does it cost to add an ADU for a family member in Orange County?
About $60,000 to $120,000 for a junior ADU, $100,000 to $250,000 for a conversion, and $250,000 to $350,000 for a detached unit.
Can my parents live in an ADU on my property?
Yes. California law doesn’t restrict who lives in an ADU, and there’s no owner-occupancy requirement for the ADU itself.
Do multigenerational homes hold their value?
A permitted ADU tends to add value and widens the buyer pool to both families and investors.
Find the Right Home for Your Family
Every family’s setup is different. I’ll help you decide between a house with an existing ADU, one with room to build, or a lot where two detached units fit after 2027, and run the numbers for each.
👉 Book a buyer ADU consult call to go through your options with Dylan
Prefer to talk now? Call Dylan Serna, ADU Realtor at 714-860-2868.
Dylan Serna | The ADU Realtor | eXp Realty | DRE #02217359
This post is general information, not legal, tax or lending advice. Costs and payments are illustrative 2026 estimates.
