Can Building an ADU Save Your Family Money Compared to Renting or Buying?

By Buz Artiano, BuildX | March 2026

Watch: Why Renting Wasn't an Option Anymore

Your daughter and her partner have been renting for two years. Every month they are throwing their money away to a landlord. They've been looking for a starter home, but every property in their price range needs a new roof, a new septic system, and new windows before it's ready to be lived in. The math just isn't working out with their finances. Renting is expensive, but buying is even worse, and the homes that are available in the area are not in liveable condition until major renovations have been done, which adds a whole new budget on top of the purchase price.

My name is Buz Artiano, and I am the founder of BuildX. We've built dozens of ADU projects across Massachusetts, mostly around the South Shore and Plymouth County areas. We are the only team you need, we handle design, permitting, and construction. So we see every phase of a project from the first site visit up until you move in. We deal with septic constraints, zoning issues, and the state's new ADU laws. About 20 percent of the families we meet with are in this same situation. There's a young adult who wants their first home but there's nothing affordable on the market. Sadly, we hear this same story at least once every week.

This article breaks down the real math and basic numbers behind the three main options for housing as a young adult in Massachusetts. Those options are continuing to rent, buying a fixer-upper, or building an ADU on a family member's property. We're gonna walk you through the costs of each one, so you understand what you get for your money, and what other families like the Cregans in Plymouth chose when they were facing the same decisions.

Does an ADU Actually Save Money Compared to Renting?

The short answer is yes, for most families who are in the same type of situation that we just talked about. But the savings don't come from the ADU being cheap. It's because other options can get outrageously expensive.

We've talked to hundreds of Massachusetts families about ADUs, and we figured out that the typical young adult renting in Plymouth County, South Shore, or southeastern Massachusetts is paying somewhere around $3,000 to $3,500 per month. That adds up to around $36,000 to $42,000 a year in rent, and none of that gives you anything to show, no equity whatsoever. Renting doesn't create an asset for you, you have very little control over when rents go up, leases end, or landlords sell the property.

Kevin and Terry Cregan, BuildX clients in Plymouth, saw their daughter and her spouse go through that exact scenario. Terry told us the family had been renting for a couple of years, but it was just so expensive. Every home for sale that was in their budget range needed a new roof, a new septic, and new windows just to make it liveable. There was just nothing on the market that was halfway decent for a price they could afford.

So, like a lot of Massachusetts families, they wondered what would happen if they stopped trying to find decent housing in a market that didn't have any in their budget and just built something on property they already owned.

What Does It Actually Cost to Build an ADU in Massachusetts?

Before we show you the hard numbers, you need to understand what's behind the ADU costs. There's three things that have the most impact on the price of an ADU. The first one is septic and utility connections: this one is the biggest unknown on any project and sways the price a lot. Second is site conditions, things like slope, ledge, drainage, and access. The last one is the size and finish level of the unit. Massachusetts allows up to 900 square feet by right under the Affordable Homes Act. You can review the full requirements at mass.gov. A one-bedroom unit on a clean lot with good soil will cost quite a bit less than a two-bedroom on a ledge-heavy lot that needs a new septic system.

As of March 2026, BuildX publishes clear pricing for every floor plan on our website. These are complete, all-in numbers that include design, permitting, site work, construction, and finishes. Here's a look at what some of our pricing looks like:

*Turnkey pricing as of March 2026. Includes design, permitting, site work, foundation, construction, and finishes. Septic work, if required, is evaluated and priced separately based on soil testing and Board of Health requirements. Current pricing is at buildx.com/adu-floor-plans/.

We wanted to put the real numbers out there because too many families get caught by fake lowball quotes. We've talked to multiple families who thought they were building a $250,000 ADU and ended up closer to $400,000 when it was all said and done. That doesn't happen by accident, it's how shell pricing is designed to work. The ads that promise $49,000 or $99,000 or $149,000 ADUs leave out everything that actually costs money. The things that take up a huge chunk of an ADU cost are site prep, foundation, utility connections, permitting, finishes, and septic. Our prices have all of that figured in.

What Does It Cost to Keep Renting or Buy a Fixer-Upper?

To understand whether an ADU saves money, you have to compare it honestly against the other two main alternatives for housing.

Renting. At $3,000 to $3,500 per month, a young couple in Plymouth County gives $36,000 to $42,000 of their money every year to a landlord. Over five years that's $180,000 to $210,000 of their money gone with nothing to show for it. There's no asset, and still zero control over whether the lease gets renewed or the rent increases. Families come to us saying they are just throwing away $40,000 a year. It's just going right into the landlord's pocket. They're not building any equity.

Buying a fixer-upper. The Cregan family actually tried to go this route first. But every home for sale that was within their daughter's budget needed a new roof, new septic, and new windows. Even if you can qualify for a loan big enough to purchase the home, the renovation costs are going to add another $50,000 to $100,000 or more on top of that. Terry Cregan said there was just nothing on the market that would work. That's the reality in Massachusetts right now: starter homes are not available at a starter price. And the entry-level homes that are out there need so much work and maintenance that it ends up out of budget.

Building an ADU. A one-bedroom BuildX ADU starts at $284,301. If the family already owns the land (like a parent's backyard or a sibling's property), then you don't have to pay for a new piece of land. Monthly payments depend on how you finance it, but families using home equity or construction-to-permanent loans usually end up paying less per month than the current rental prices in the area. Plus, every payment is building equity in a real asset. Our all-electric, high-efficiency construction also keeps the utility bills very low. In our Plymouth projects, the average electricity bill for a two-to-three person household in an ADU has been around $275 per month.

Why Did the Cregans Choose an ADU Over Renting or Buying?

Kevin and Terry Cregan are BuildX clients in Plymouth. They're building a detached ADU for their daughter and her spouse, who can't afford anything on today's market. Their family is going through the same decision process that thousands of other Massachusetts families are going through right now.

First, they tried buying, but they couldn't get that to work. Since they weren't able to buy something they had to keep renting and the rent just keeps going up and up. So Terry started researching their other options online. She looked at traditional builders first but she was less than impressed with the level of communication. She also checked out those modular ADUs, researching every type of prefab unit that could be dropped onto a lot. Unfortunately none of them met her standards. The last thing she did was a deep search for ADUs in Plymouth and that's how she found BuildX, because we built Plymouth's first ADU.

Kevin and Terry went to a BuildX open house right down the street. Kevin said the people who work for BuildX were great, they were very helpful, very knowledgeable, and they weren't trying pushy sales techniques. That first impression, combined with our track record as Plymouth's first ADU builder, is what made them choose us to build their ADU.

The financial side of things was pretty simple because the Cregans own land. Their daughter was paying rent and building no equity. Every month she was losing money. By building an ADU on property they already have, the family can turn that rent expense into an asset. The daughter and her spouse get their own home, Kevin and Terry keep their family close, and the property now has another home on it that adds long-term value.

What Costs Do Most Families Miss When Comparing Options?

The biggest mistake families make when comparing an ADU to renting or buying is looking only at the sticker price. They see a $254,000 ADU and a $350,000 fixer-upper and assume the house is the better deal because it comes with land. But you have to compare three major things when looking at an ADU, it's not only about the advertised price.

First, with an ADU the land cost is already solved. If a parent or sibling owns a property with room for a detached structure, the family doesn't have to buy another piece of land. So that takes the biggest expense off the table.

Second, the real cost of the fixer-upper house is a lot more than the list price. A $350,000 home that needs $80,000 in repairs is a $430,000 home. And you have no choice but to spend that $80,000 upfront and immediately because you can't move into a house with a failed septic system or a roof that leaks. The Cregans did their research and saw that every property in their daughter's budget wasn't livable without expensive renovations.

Now the third thing is something that most people don't even think about, but it's important. A brand new ADU has zero deferred maintenance. When we build a unit, the roof is rated for 30 to 50 years and all the mechanicals like HVAC systems are brand new with warranties. The insulation is of good quality that meets all the current energy codes and the heat pump system is high efficiency. That means you're not having to deal with someone else's problems. With a fixer-upper, you're buying the house and you're buying all the DIY or shortcuts the last owner made. We evaluate every site before we quote, and we include septic, foundation, utility connections, and finishes in our published pricing specifically because we've seen so many people get totally blindsided by costs that other builders leave off the quote when they talk to you.

Is an ADU the Right Move for Every Family?

No, and it wouldn't be honest to say it was. An ADU makes financial sense when a family member already owns a property with enough room and the right conditions for a detached unit. If nobody in the family owns land in Massachusetts, or if the property can't support more load on the septic, or if the lot's setback requirements leave no room to build it, then the ADU path may not work.

There are also families who are better off renting in the short term. If you think you might be moving to a different area within a year or two, locking into an ADU on a family property doesn't really make sense. If you think your family dynamics are not right for sharing a property or that it might become overly complicated, we need to talk about that before construction.

We should also tell you that building an ADU strictly as a rental investment in suburban Massachusetts will hardly ever give you a decent return on your money. If the construction cost is upwards of $250,000 and the rental market supports $2,000 to $2,500 per month, that return is very low. ADUs make the most sense when they are built for a family member who's living somewhere that they can no longer afford. They are not ideal as purely a source of income.

Who Is Actually Building ADUs in Massachusetts Right Now?

Based on hundreds of consultations with Massachusetts families, the numbers are pretty consistent. Approximately 60 percent of the families we work with are parents preparing for a big change. Either the parents are downsizing into the ADU so the children can take the main house, or the children are buying the family home and building an ADU in the backyard for aging parents. Another 15 to 20 percent are families with a member who has a disability or needs ongoing support. And the remaining 20 percent are young adults, like the Cregans' daughter, who want their first home and can't find anything they can afford in the Massachusetts housing market.

Massachusetts is approximately 200,000 homes short of what the state actually needs. Young adults are leaving the state because they can't afford to stay. The Affordable Homes Act made ADUs legal by right on single-family lots statewide so that it starts making a dent in this housing shortage. For families who already own property, building an ADU is the fastest way for a family member to have an affordable place to live, on land they already have, without having to deal with a housing market that doesn't give your average first time home buyer any good options.

Your Family Has Options Beyond Renting and Competing for Overpriced Homes

The Cregan family tried all the normal routes before they found the one that worked. Renting was a dead end and the starter home market was full of properties that cost more to fix than to buy. The ADU gave them a new home on family land, built to current standards, with a monthly cost that was easily manageable and the payments now going toward equity.

If your family is running the same numbers, the question is not whether you can afford an ADU. It is whether you can afford to keep paying rent.