ADU (in-law unit) build: DIY runs ~$110,000 in 8–12 mo, pro install $245,000 in 8–12 mo. National Cost-vs-Value ROI: 65%.
8–12 mo of your weekends
8–12 mo, turnkey
Save 25–35% vs full pro
~$38,000 in transaction costs
Here's what the math looks like for ADU (in-law unit) build as of 2026-05-25. The cheapest of the 4 options we compared is Move instead at roughly $6,333/mo all-in, and the priciest is Hire a pro at $40,833/mo. That's a monthly spread of $34,500 — money that compounds fast when you're talking five-year and ten-year horizons.
Where it gets interesting is the wealth side. Over five years, DIY builds the most net worth ($49,000) thanks to a mix of equity, appreciation, and avoided sunk cost. The worst-performing path leaves you about $135,000 behind it. That gap is why "which is cheaper this month" is the wrong question. The right one is "which path puts me ahead five years out, given my actual scenario and my own risk tolerance?"
Below we walk through each option with the local numbers we pulled for ADU (in-law unit) build, then three plug-and-play scenarios you can run before you commit to anything.
Every scenario we publish gets its own data sheet because the answer genuinely changes by location. For ADU (in-law unit) build, the specifics that move the needle are: DIY cost $110,000, Pro cost $245,000, Time to complete (DIY) 8–12 mo, Resale ROI 65%, Added home value $159,000. A national-average calculator that ignores those inputs will lie to you about ADU (in-law unit) build specifically — sometimes by tens of thousands of dollars over a five-year window.
That's why this page isn't a wrapper around a generic spreadsheet. The four (or five) option columns above are running on ADU (in-law unit) build's actual property tax rate, transit fare, median rent — whatever applies to this hub. If something looks off versus what you're seeing on the ground, that's useful signal: scroll to the methodology section, check our sources, and tell us what we missed. We update these numbers on a published cadence and credit the contributors who spot drift.
DIY — 8–12 mo of your weekends. Roughly $18,333/mo all-in with $110,000 upfront. After five years our model projects a net-worth delta of $49,000 versus a do-nothing baseline. Where it wins: Cheapest cash outlay; Full control over quality; Adds equity faster vs cost. Where it bites: 8–12 mo of your life; Mistakes cost real money; No warranty on labor.
Hire a pro — 8–12 mo, turnkey. Roughly $40,833/mo all-in with $245,000 upfront. After five years our model projects a net-worth delta of -$86,000 versus a do-nothing baseline. Where it wins: Done in days not months; Warranty + insurance covered; Quality you can resell. Where it bites: $135,000 premium vs DIY; Scheduling lag of 6–12 wks; Change orders add 15–25%.
Hybrid (you demo, pro finishes) — Save 25–35% vs full pro. Roughly $29,583/mo all-in with $171,500 upfront. After five years our model projects a net-worth delta of -$12,500 versus a do-nothing baseline. Where it wins: Splits the cost-vs-time gap; Pro warranty on finish work; Less downside on quality. Where it bites: Two schedules to coordinate; Pro may charge extra to fix your demo; Permit + inspection still required.
Move instead — ~$38,000 in transaction costs. Roughly $6,333/mo all-in with $38,000 upfront. After five years our model projects a net-worth delta of $9,700 versus a do-nothing baseline. Where it wins: No reno headache; Get exactly what you want; Often closes in 60 days. Where it bites: 6% realtor + 2–3% closing = $38,000; Lose your interest rate; Moving costs $3–10k.
Conservative — assume things go sideways. Use the lower end of every input. Income flat for five years, no appreciation, maintenance comes in 30% over your initial estimate, and you stay put the full term. In this scenario the option with the lowest *combined* monthly + opportunity cost usually wins, even if it's not the headline-cheapest one. For ADU (in-law unit) build, that's typically Move instead — but only if the five-year net-worth delta is within $33,750 of the leader; otherwise the equity gap closes the case.
Typical — assume the base rate. Plug in the median figures shown on this page. This is what a representative household in ADU (in-law unit) build actually experiences, not a best-case projection. We bias these inputs slightly conservative on appreciation and slightly aggressive on maintenance because that's where most calculators fail people in practice.
Ambitious — assume things break your way. Raise your income trajectory, drop your move-out horizon to three years, and let appreciation run at the upper end of ADU (in-law unit) build's historical band. In this case the equity-building options (typically DIY) pull ahead hard — often by enough that the higher monthly carry pays for itself before year four. The watch-out: ambitious scenarios assume you actually execute. If you're not sure you'll stay, the conservative path is the honest pick.
- Cost-vs-Value Reports show adu (in-law unit) build returns about 65% at resale — meaning you lose ~$86,000 of the $245,000 spent if you sell within 2 years.
- Bid spread on a ADU build is typically 35–60% — get three quotes, always. The cheapest bid is rarely the best value and the most expensive is rarely the highest quality.
- DIY savings on this project are real but assume you don't break anything expensive. Add a 20% materials buffer to your DIY budget.
- If you're financing, HELOC + project loan combined add 6–9% effective APR — bake that into your ROI math, not just the sticker price.
None of these are unique to ADU (in-law unit) build alone, but they hit harder here than the national average because of the specific cost structure we documented above. The save-scenario feature on this page is built precisely so you can capture a "before I forget" snapshot of your numbers and compare against your real bank-statement reality six months later.
Cost estimates: DIY = materials + permit + tool rental (national median per HomeAdvisor); Pro = total project median from Remodeling Magazine Cost vs Value 2024; Hybrid = materials + 70% of pro labor; Move = 6% agent commission + 2.5% closing + $5k physical move on a median-priced home. ROI = added-resale-value / cost-paid using NAR Remodeling Impact Report estimates. Five-year net worth delta = added value − cost paid, treating renovation as a partially-recouped capital expense and a move as a transaction-cost write-off.
Specifically for ADU (in-law unit) build, the inputs above come from: Remodeling Magazine, 2024 Cost vs Value Report; HomeAdvisor / Angi 2024 True Cost Survey; National Association of Realtors, 2024 Remodeling Impact Report; U.S. Census Bureau, American Housing Survey 2023; Freddie Mac PMMS, mortgage rate baseline. Where two reputable sources disagreed we used the more recent figure and noted the prior value in our changelog. We don't accept paid placements on these pages — affiliate disclosure lives on the editorial-policy page in the footer.
Last reviewed 2026-05-25. If you spot a number that's drifted, the "Email me this result" button on each option sends us a copy along with whatever you flagged.
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Remodeling Magazine's 2024 Cost vs Value Report puts the recoup ratio on a ADU build at about 65%. That means on a $245,000 project you'll likely add ~$159,000 to your home's value. Most of the value here is enjoyment, not resale.
DIY-ing this project saves about $135,000 (55%) but takes 8–12 mo. The right call depends on whether your hourly opportunity cost is below ~$1688/hr. If yes, DIY. If your evenings are worth more than that, pay the pro.
Hybrid (you demo + paint, pro does plumbing/electrical/structural) usually splits the difference — saves about 25–35% vs full pro on a ADU build and still gets you a warranty on the load-bearing work. Coordination overhead is the catch; build in a 2-week buffer between phases.
Moving costs (6% agent + 2–3% closing + ~$5k physical move) total about $38,000 on a median home. If your project budget exceeds that AND you'd be okay losing your current interest rate, moving is worth considering. If you're already happy with the home otherwise, the math almost always favors renovating.
Pro: 8–12 mo once they break ground. DIY: 8–12 mo of nights and weekends. Permit/inspection lead times add 2–6 weeks before either starts. Plan for the project to take 1.4× your initial estimate — that's the empirical average from HomeAdvisor's owner-completed survey.