Assisted Living vs. an ADU in New Hampshire: The Real 10-Year Cost Math

Over ten years, assisted living for one parent in New Hampshire can easily consume more than the entire cost of building an accessory dwelling unit in your backyard — several times over. Commonly cited industry surveys put NH assisted living at roughly $70,000 to $100,000+ per year, while a typical NH ADU build runs $275,000 to $400,000+ one time, and your family keeps the building as equity when it's done.

That's the short answer. The longer answer is worth walking through carefully, because the two options aren't just different price tags — they're different kinds of spending. One is rent that disappears every month. The other is construction cost that turns into an asset on your own property. Here's the math, and the parts of the decision the math can't settle.

How much does assisted living cost in New Hampshire?

New Hampshire is consistently one of the more expensive states for senior care. Commonly cited industry surveys place assisted living here in the range of $70,000 to $100,000+ per year, depending on the community, the apartment, and the level of care your parent needs. Treat any specific quote you receive as a starting point, not a ceiling:

• Base rates typically cover housing, meals, and a baseline of support. Additional care — medication management, mobility help, higher acuity — is usually billed on top.
• Costs tend to move in one direction over time, both because rates rise and because care needs deepen.
• Memory care, where needed, generally costs meaningfully more than standard assisted living.

None of that is a knock on assisted-living communities, many of which provide excellent care. It's just the honest shape of the expense: large, recurring, and likely to grow.

How much does an ADU cost to build in NH?

A typical New Hampshire ADU — a self-contained apartment with its own kitchen, bath, and entrance, attached to your home or detached in the yard — runs $275,000 to $400,000+ depending on size, site conditions, and finishes. Use $300,000 as a working number for a well-built, single-level unit designed for aging in place.

That's real money, and it's mostly spent up front. But it buys a fundamentally different thing than a year of assisted living buys:

• It's a one-time cost, not an annual one.
• It's attached to property your family owns. When your parent no longer needs it, the unit doesn't vanish — it becomes a rental, a home office, guest space, or housing for the next family member who needs it.
• It's built to your parent's actual needs: zero-step entry, wide doorways, a walk-in shower, and their own front door fifty feet from yours.

Where's the break-even point?

Take the $300,000 worked example against the commonly cited $70,000–$100,000 annual range. The build cost equals roughly three to a little over four years of assisted-living payments. A larger or more complex build at the top of the construction range pushes break-even out toward the five-year mark. Either way, the crossover arrives startlingly fast for a decision families often frame as "we can't afford to build."

Two honest caveats on that framing:

• The math above assumes cash. If you finance the build, interest changes the picture, and how much depends entirely on the rate environment when you borrow. In a high-rate period, financing costs stretch the break-even timeline; in a lower-rate period, less so. Run the numbers with a local lender using today's actual rates, not a blog post's.
• Assisted living isn't a fixed number either. The annual figure you're comparing against tends to climb over a multi-year stay, which generally moves break-even earlier, not later.

What does the 10-year picture look like?

Stretch the comparison to a decade — a realistic horizon for a parent who moves in at, say, their late seventies.

• Assisted living: at $70,000 to $100,000+ per year, ten years of payments lands in the high six figures to over a million dollars. At the end, the money is spent and there is nothing to show for it on your balance sheet.
• The ADU: the $275,000–$400,000+ went out once, years ago. The unit is still standing on your property. Whether it ultimately rents to a tenant, houses another relative, or simply transfers with the home when you sell, the value stays in the family rather than leaving it. How much a finished ADU adds to your specific home's appraised value varies by property and market — but "an additional dwelling on the lot" is not worth zero, and the payments you didn't make to a facility are the larger prize anyway.

The 10-year comparison isn't close on dollars. Which is exactly why the non-dollar factors deserve equal weight.

What does the money math leave out?

An ADU is not the right answer for every family, and pretending otherwise would be doing you a disservice.

• Care level is the deciding factor. An ADU keeps a parent near care — yours — but it doesn't provide clinical care. For a parent who needs round-the-clock skilled nursing or advanced memory care, an ADU plus in-home help may not be enough, and a licensed facility is the responsible choice.
• You become part of the care plan. Proximity is the ADU's greatest feature and its greatest demand. Be honest about your household's capacity, and price in-home aides into your comparison if daily help is likely.
• Independence and dignity cut the other way. Many parents dread the institutional move above all else. A private cottage in a grandchild's backyard is a very different tenth decade than a unit down a carpeted corridor.
• Timing matters. Design, permitting, and construction take months, not weeks. This is a plan you make ahead of the crisis, not during it.

How do families actually pay for the build?

Most families don't write a $300,000 check. Common routes include a HELOC or home-equity loan against the main house, a cash-out refinance, or a construction loan that converts to standard financing when the unit is finished. Some lenders will also count projected rental income from the ADU when qualifying you — useful if the long-term plan is tenant income after your parent no longer needs the unit. Terms and rates vary widely and shift with the market, so talk to a local lender who knows ADUs before you assume anything about affordability.

Can you even build one in your town?

In New Hampshire, yes — this question got dramatically easier. Since July 1, 2025, under RSA 674:72 (amended by House Bill 577, 2025 Chapter 197), every NH town must allow one ADU — attached or detached — by right wherever single-family homes are permitted. No variance, no special exception, no zoning-board hearing for the ADU itself; you pull a normal building permit and meet ordinary standards like setbacks and septic capacity. Towns may cap ADU size, but never below 750 sq ft, and may require at most one extra parking space — which you can provide on-site or off-site, your choice. Even converting an existing garage is protected, whether or not it meets today's setbacks. The full statewide picture is in our NH ADU law guide.

Details still vary town to town — Manchester, for example, allows one ADU by right up to 950 sq ft, with rules confirmed directly with the town. Our guides and county pages like Hillsborough County break down size caps, parking, and owner-occupancy rules for each covered town, including where a town's posted ordinance is superseded by the 2025 law.

Run your own numbers, be honest about the care your parent needs — and notice that the option that keeps the family close is also the one that keeps the money in the family.