Lately, I've been hearing the same question from a lot of buyers.

"Sean, can I build a rental unit on the property if I buy it?"

Or...

"I've heard the ADU rules changed. Does that make buying a home more affordable?"

The answer is...

Maybe.

And for the right buyer, it can completely change the numbers.

Washington recently updated its ADU laws, and Bellingham has followed with changes of its own. If you're buying a home in Whatcom County, these new rules create opportunities that simply didn't exist a few years ago.

Let's talk about what changed—and why buyers are paying attention.

First...What Exactly Is an ADU?

An ADU, or Accessory Dwelling Unit, is simply a second living space on a property.

It could be:

• A backyard cottage
• A finished basement apartment
• An apartment above a garage
• An attached guest suite
• An in-law apartment

Whatever you call it, the idea is the same.

It's a separate living space that can provide housing for family members—or generate rental income.

So What Changed?

This is the part that's getting everyone's attention.

Washington State passed HB 1337, and Bellingham updated its local regulations to make ADUs easier to build in many situations.

Some of the biggest changes include:

• You can now have up to two ADUs on many single-family lots.
• Owner occupancy is no longer required in most situations.
• Each ADU can be up to 1,000 square feet.
• Some residential areas may now allow significantly more housing density than before.

Now, that doesn't mean every property qualifies.

Zoning still matters.

Lot size still matters.

And if you're buying near the Lake Whatcom watershed, there are additional restrictions you'll want to understand before making plans.

That's why I always encourage buyers to verify what's allowed on a specific property rather than assuming every lot is the same.

Why Buyers Are Suddenly Interested

Honestly...

It's not because everyone suddenly wants to become a landlord.

It's because housing has gotten expensive.

If you've been shopping for homes in Bellingham lately, you already know that.

Many buyers are looking for creative ways to make the monthly payment more manageable.

That's where an ADU can become really interesting.

Imagine purchasing a home and adding a detached backyard cottage that rents for $1,500 a month.

Or buying a property that already has a legal basement apartment producing income.

Suddenly, the monthly numbers may look very different.

For some buyers, that rental income can make homeownership much more realistic.

Existing ADU or Future Potential?

I usually encourage buyers to think about this in two different ways.

Option One: Buy a Home That Already Has an ADU

This is often the simplest path.

The work has already been done.

Depending on your loan program, your lender may even allow some of that existing rental income to help you qualify.

Every loan is different, so it's worth having that conversation early.

Option Two: Buy a Property With Room to Build One Later

This option gives you flexibility.

Maybe you don't need the extra income today.

But a few years from now?

Life changes.

You might have aging parents.

Adult children moving back home.

Or maybe you'd simply like an additional source of income.

Having that option can add long-term value to the property.

A Few Things I'd Want You to Know

Before you get too excited, there are a few realities.

Building an ADU isn't inexpensive.

You'll still need permits.

Construction costs are significant.

Utility connections can add expense.

And not every lot will qualify.

That's why I always tell buyers not to fall in love with the idea before we verify what's actually possible.

A quick conversation now can save a lot of frustration later.

What If You're Selling?

If your property already has a permitted ADU—or has strong potential for one—that can absolutely be an attractive feature in today's market.

More buyers are actively searching for:

• Multi-generational living
• Rental income opportunities
• Long-term investment potential

Those features weren't nearly as common five years ago.

Today, they're becoming a major selling point.

That said, if your ADU isn't permitted, or if you're advertising future development potential, it's important to be accurate.

Every property is different, and buyers are doing their homework.

My Advice

One of the biggest mistakes I see buyers make is assuming every property has the same potential.

They don't.

Some lots are fantastic candidates for an ADU.

Others aren't.

Before you make an offer because you're imagining a future rental unit, let's verify what's actually allowed.

That's a much better conversation to have before you're under contract than after you've already fallen in love with the house.

Thinking About Buying in Bellingham or Whatcom County?

If you're considering a property because of its ADU potential—or you're wondering whether an existing ADU changes the value of a home—I'd be happy to help you evaluate the possibilities.

We'll look at zoning, neighborhood, resale value, rental potential, and whether the property fits your long-term goals.

No pressure.

No obligation.

Just honest advice so you can make an informed decision.

—

Sean Hackney
NextHome NW Living
Bellingham & Whatcom County Real Estate