If you own a home with extra space, you might be sitting on an income opportunity you have not fully used yet.
One of the most practical strategies right now is an adu rental. It can help you bring in monthly income, add value to your property, and create more housing without buying another house.
This is not a get-rich-quick thing. It’s a long-term play that can be simple if you follow the rules in your city and run the numbers carefully.
Let’s walk through what ADUs are, how they work, and why some investors are treating them as one of the best ROI moves in today’s market.
An ADU is an Accessory Dwelling Unit. That’s a smaller home on the same property as a main house. It usually has its own:
Common ADU types include:
The main reason ADUs are growing is simple: many cities need more housing, and they are allowing homeowners to add it without tearing down neighborhoods.
Most people think it’s just “build a small unit and rent it.” That is the idea, but the details matter.
Before you spend money on plans, find out what your city allows. Rules can cover things like:
If the rules are unclear, talk to your local planning office. That one conversation can save months of frustration.
When you’re building an adu, design choices can make or break the rentability.
A small unit feels better when it has:
You do not need luxury finishes. You do need durable finishes and a layout that feels comfortable.
Costs vary by area. They depend on:
A safe approach is to budget for surprises. Almost every project has them.
On the DealMachine REI Podcast, Thach shared a story that helps explain why ADUs can be so powerful, especially in high-cost cities like Seattle.
One of his investment types is single-family homes, where he can add one or more units. His focus is not just on buying a house. It’s buying a property where the land gives him options.
Thach shared that he targets ugly houses on lots that give him room to add value. Details he looks for:
This is a good reminder: the deal starts with selection. ADUs work best when the property is a fit from day one.
Thach gave a clear example:
That’s a big deal because many investors assume high-cost markets can’t hit strong rent-to-cost ratios. His point was that adding the unit can change the math.
He even mentioned the “1% rule” idea showing up in an expensive neighborhood because the unit was added value, not bought as a separate property.
Thach compared ADUs to buying large multifamily deals in today’s rate environment. His view was:
His preference was to focus on deals that can cash flow now, even with higher rates, and then refinance later if rates drop.
That’s a calm, sustainable approach. It’s not flashy, but it’s how people build wealth without constantly feeling pressure.
Thach also mentioned something important: some states are moving toward allowing ADUs to be sold separately from the main home, in certain situations.
He called out Washington and California as places where this has been possible in some form, and he expects other states to follow over time.
Even if you never plan to sell separately, policy trends matter because they can increase demand and support property values.
Check out the full episode with Thach Nguyen below.
Not every property should have an ADU.
Before you commit capital, walk through this checklist.
Start with the basics:
Even strong deals fall apart if zoning blocks you.
Some cities are moving faster than others when it comes to density. The more flexible the local policy, the more viable the long-term play.
Access matters more than most people think.
Look for:
You want a unit that feels private and functional. A poorly placed unit can hurt rent potential.
When building an adu, design and placement impact both rent and resale value.
Construction costs vary by market. Labor, permits, materials, and utility connections all add up.
Your underwriting should include:
A tight budget with no margin creates stress. Conservative numbers create stability.
ADUs work when discipline stays in place. They fail when emotion replaces math.
Here are the most common mistakes:
1. Overbuilding for the Area
Luxury finishes in a workforce rental neighborhood rarely produce proportional rent increases. Build for durability and functionality.
2. Ignoring Utility Costs
Separate meters versus shared utilities can change operating expenses. Know how billing will work before construction begins.
3. Underestimating Timeline
Permits can take months, depending on the city. Cash sitting idle without planning can reduce returns.
4. Assuming Appreciation Will Save the Deal
The numbers must work based on rent and cost. Appreciation is upside, not the strategy.
The real power of an ADU strategy shows up over time.
A disciplined approach looks like this:
This is not a fast flip strategy.
It is a long-term wealth strategy.
One property becomes two income streams. Two streams improve leverage. Leverage supports the next acquisition.
That compounding effect is what separates activity from real growth.
Markets shift. Rates move. Headlines change.
But adding usable housing where it is needed remains a strong long-term principle.
An ADU strategy is not about chasing trends. It is about creating income, building equity, and controlling risk through thoughtful development.
When the property fits, and the numbers make sense, it can turn one asset into something far more durable.