Fullerton ADU Properties — Market Update (March 2026)
Seven ADU properties in Fullerton right now. Three are still active, four have already sold. What stands out about Fullerton compared to other OC cities is the mix — you have single-family homes with ADUs sitting next to duplexes, and the price spread is massive. Here is the full breakdown.
Sold
128 S Citrus AVE — $1,400,000 7 bed / 4 bath · 2,431 sqft · Built 2025 · Lot: 7,425 sqft · $575/sqft
This is the one worth paying attention to. A brand-new 2025 build with 7 bedrooms and 4 baths at $575 per square foot — the lowest price per square foot of any listing on this sheet. The property sold tenant-occupied with two separate entrances, which tells you exactly how this was designed: a main home and a fully independent rental unit operating under one roof. This is the textbook ADU-for-cash-flow play. The tenant was already in place at close, meaning the buyer walked into day-one income. At $1.4M with rental income from the ADU unit, the numbers on this one pencil well for an investor, especially at Fullerton's lower entry point compared to coastal OC cities. New construction at this price in a city where the median sits around $1.08M is a signal that ADU properties are trading at a premium — but a justified one when the income is documented and immediate.
124 N Princeton AVE — $1,100,000 (Duplex) 5 bed / 2 bath · 1,804 sqft · 1975 · Lot: 6,408 sqft · $609/sqft
A duplex that sold at $1.1M and the lowest total price on this list. Five bedrooms and two baths across two units on a 6,400 sqft lot. At $609/sqft, this is priced right for an investor looking at Fullerton's rental market. The duplex format is essentially two rental units already configured — no ADU construction needed. This is a buy-and-hold cash flow play from day one.
725 San Ramon — $1,449,000 (Duplex) 5 bed / 2.5 bath · 2,441 sqft · 1978 · Lot: 7,972 sqft · $593/sqft
Another duplex sale, this time on a larger lot at nearly 8,000 sqft. The price per square foot at $593 is the second lowest on the list, which makes sense for a duplex — you are buying for income, not for finish quality. The lot size here is interesting. At 7,972 sqft with a 1978 duplex, there could be room for a JADU or even a detached ADU addition depending on the existing footprint and setbacks. That would turn a 2-unit property into a 3-unit property on a single lot in a city that is ADU-friendly.
660 Green Acre DR — $2,625,000 5 bed / 4 bath · 3,645 sqft · 1961 · Lot: 20,700 sqft · $720/sqft
This is the opposite end of the spectrum. A half-acre lot with a 3,645 sqft home that sold at $2.625M. Five bedrooms and four baths on 20,700 sqft of land — this is a luxury ADU configuration where the additional square footage is designed for the owner's use, not for generating rental income. The lot size alone offers significant development potential, but the buyer at this price point is likely an end-user, not a cash flow investor. This property also demonstrates what happens to price per square foot when the land is the primary value driver — $720/sqft is well above the duplex sales but still below the coastal OC averages.
Active
139 Ramona DR — $1,375,000 (Trust Sale) 4 bed / 3.5 bath · 1,915 sqft · 1939 · Lot: 7,274 sqft · $718/sqft
A trust sale on a 1939 home with nearly 7,300 sqft of land. Trust sales often come with less seller flexibility on repairs and disclosures, but they can also mean motivated pricing. At $1.375M with 4 beds and 3.5 baths, the bedroom-to-bathroom ratio suggests this property has been reconfigured at some point — a 1939 home does not come standard with 3.5 baths. The lot size supports an ADU addition, and the trust sale dynamic means there could be room to negotiate below asking.
151 N Lincoln — $1,350,000 (Duplex) 4 bed / 4 bath · 2,188 sqft · 1898 · Lot: 6,098 sqft · $617/sqft
The oldest property on this list by a wide margin — built in 1898. A duplex at $1.35M with 4 beds and 4 baths across the units. At $617/sqft, it is priced in line with the other duplex sales. The age of the property is the variable here. An 1898 structure is going to have significant maintenance considerations, and any lender is going to scrutinize the condition closely. For a cash buyer comfortable with older properties, the income potential is there. For a financed buyer, this one requires a closer look at the inspection.
1419 N Richman Knoll — $3,500,000 6 bed / 4.5 bath · 4,351 sqft · 1963 · Lot: 50,302 sqft (1.15 acres) · $804/sqft
The standout listing. This is sitting on over an acre of land — 50,302 sqft — which is rare for Fullerton. Six bedrooms and 4.5 baths across 4,351 sqft at $3.5M. At this lot size, the ADU potential is essentially unlimited from a space perspective. You could build a full 1,200 sqft detached ADU and barely notice it on the property. But at $3.5M, this is a luxury estate buyer, not a cash flow investor. The ADU here is about optionality — guest house, multigenerational living, or future rental income if the owner decides to monetize the space down the road.
What This Market Is Telling Us
Four out of seven already sold — that is strong absorption. In a market where the typical Fullerton home is sitting for 37 days, having more than half of the ADU inventory already closed tells you this product type is moving. ADU and multi-unit properties in Fullerton are not sitting.
The entry point in Fullerton is significantly lower than coastal cities. The median home price in Fullerton is around $1.08M, and the ADU properties on this list start at $1.1M for a duplex. Compare that to Costa Mesa where ADU properties are starting closer to $1.3M and running up to $3.7M. For investors who want to get into the ADU space in Orange County without the coastal premium, Fullerton is one of the strongest options.
Duplexes are dominating the multi-unit inventory. Three of the seven properties on this list are duplexes. That is significant because duplexes in Fullerton represent an investor play that does not require new construction — the units are already built, already configured for rental, and already generating income. For an investor who does not want to deal with the permitting and construction timeline of building an ADU from scratch, a Fullerton duplex in the $1.1M–$1.45M range is a turnkey alternative.
128 S Citrus is the template for new-construction ADU investing. A 2025 build, tenant-occupied, two separate entrances, 7 beds and 4 baths, sold at $1.4M. That is what a purpose-built ADU investment property looks like in execution. The buyer got a brand-new home with an income-producing unit already occupied. No construction risk, no permit timeline, no vacancy on day one. Properties like this are exactly what experienced ADU investors are hunting for — and the fact that it sold confirms the demand is real.
The luxury end is a different conversation. The 660 Green Acre sale at $2.625M and the 1419 N Richman Knoll listing at $3.5M are not cash flow plays. These are properties where the ADU adds lifestyle value — a guest house, home office, or multigenerational space. The buyer pool for these properties is smaller but willing to pay significantly more per square foot. If you are a seller with a luxury ADU property in Fullerton, pricing strategy matters more here than anywhere else on this list because the comp pool is thin.
Fullerton vs. Costa Mesa for ADU Investing
Both cities are ADU-friendly, but they serve different investor profiles.
Fullerton offers a lower entry point, more duplex inventory, and strong rental demand driven by its proximity to Cal State Fullerton and a large renter population. The cash-on-cash math tends to look better in Fullerton because you are starting at a lower basis.
Costa Mesa offers higher rents — especially on the east side where a detached ADU can pull $3,900–$4,500/mo — but the entry price is higher and the buyer pool skews more toward lifestyle buyers alongside investors.
For pure cash flow, Fullerton is hard to beat in OC right now. For appreciation plus income, Costa Mesa's east side has the edge. Both cities are actively transacting ADU properties, which is the most important signal of all.
