Should You Build an ADU? The Real Costs, Rules & ROI in 2026

ADUs—also known as granny flats, casitas, guest houses, or backyard homes—have become increasingly popular throughout California.

If you’ve been thinking about adding one to your property, you’re probably asking the same question as many homeowners:

“Is building an ADU really worth it?”

The answer depends on your goals, budget, and how long you plan to keep your home.

What Is an ADU?

An Accessory Dwelling Unit (ADU) is a secondary living space built on the same property as your primary home. It can be a detached guest house, a converted garage, or an attached addition.

California has made it much easier to build ADUs in recent years, and many cities—including Corona and Riverside County—must approve qualifying projects that meet state and local requirements.

How Much Does an ADU Cost?

Building an ADU is a significant investment.

Today, most detached ADUs in Southern California cost between $175,000 and $350,000 or more, depending on the size, finishes, utility connections, permits, and site work. Garage conversions may cost less, while custom projects can exceed $400,000.

Many homeowners underestimate the additional costs beyond construction, such as engineering, permits, and utility upgrades.

Is an ADU Worth the Investment?

For many homeowners, the answer is yes.

A one-bedroom ADU in Corona may rent for around $2,000 per month, helping offset your mortgage, generate retirement income, or provide housing for family members.

A permitted, well-built ADU can also increase your home’s value—but not necessarily by the exact amount you spent to build it. The return depends on your neighborhood, the quality of the ADU, and buyer demand.

If you’re planning to stay in your home for several years, the long-term benefits often make much more financial sense than if you’re planning to sell in the near future.

Before You Build

Not every property is an ideal fit for an ADU.

Lot size, access, easements, utility placement, and neighborhood demand can all affect whether the investment makes sense.

That’s why it’s a good idea to speak with a local real estate expert before moving forward. A quick evaluation can help you determine whether building an ADU is the right decision for your property and your goals.

Final Thoughts

An ADU can provide rental income, increase your home’s appeal, and create valuable living space for years to come—but it’s not the right investment for every homeowner.

If you’re considering building an ADU in Corona, Eastvale, or the surrounding Riverside County communities, I’d be happy to help you evaluate your property and determine whether an ADU makes financial sense for your situation.

Contact Diana Renee Homes today for honest advice and local expertise before starting your ADU project.