San Diego multifamily investment guide

Most of the regulatory findings in this series govern what an owner may charge. This one governs what an owner may knock down, and it applies to a strip of California that contains a large share of this county's most valuable land.

Section 65590 of the California Government Code, commonly called the Mello Act, applies "within the coastal zone as defined and delineated in Division 20 (commencing with Section 30000) of the Public Resources Code," and requires each local government to comply "in that portion of its jurisdiction which is located within the coastal zone."³

Subdivision (b) is the operative rule. "The conversion or demolition of existing residential dwelling units occupied by persons and families of low or moderate income ... shall not be authorized unless provision has been made for the replacement of those dwelling units with units for persons and families of low or moderate income." The replacement units must be in the same city or county, on the site or elsewhere in the coastal zone where feasible, and "if location on the site or elsewhere within the coastal zone is not feasible, they shall be located within three miles of the coastal zone." They must be "provided and available for use within three years from the date upon which work commenced."³

The trigger is broader than it first appears. Where a unit is occupied by more than one household, the subdivision applies "if at least one such person or family, excluding any dependents thereof, is of low or moderate income." A single qualifying household in a shared unit brings the whole unit within the rule.³

Then the provision an investor should read before running any coastal redevelopment model. "If a substantial number of persons or families of low or moderate income were evicted from a single residential development within one year prior to the filing of an application to convert or demolish that structure, the evictions shall be presumed to have been for the purpose of avoiding the requirements of this subdivision and the applicant for the conversion or demolition shall bear the burden of proving that the evictions were not for the purpose of avoiding the requirements of this subdivision."³

That is a burden-shifting presumption running against the applicant. Emptying a building before filing does not remove the obligation; it creates a rebuttable presumption that you were trying to remove it, and puts the cost of disproving that on you. The obvious sequencing, buy, empty, then apply, is the sequence the statute is written to catch.

We noted the same anticipated maneuver, blocked a different way, in our Northern New Jersey guide: there, a building qualifies for the rent control exemption only if it is genuinely new construction, and the statute states that "mere vacancy shall not be considered an intervening use." Two states, the same expected behavior, two different mechanisms. Both reward the owner who does not try it.

• Applies inside the coastal zone delineated under Division 20 of the Public Resources Code.
• Conversion or demolition may not be authorized without replacement units.
• Replacement units must be available within three years of commencement of work.
• Evictions within one year before the application shift the burden onto the applicant.

Emptying the building first does not remove the obligation. It creates a presumption that you were trying to, and hands you the burden of disproving it.

In four of the large metros we have published, the core county lost residents while the surrounding ring gained them. San Diego runs the other way, and that is the most useful fact in this guide after the statute.

San Diego County fell 0.5 percent between April 2020 and July 2025, a loss of 16,400 residents. Over the same period the City of San Diego grew 1.6 percent, adding 21,625. The city gained more people than the county lost, which means the balance of the county gave up more than the city added.²

The coastal cities are part of that. Oceanside fell 2.1 percent, losing 3,675 residents. Chula Vista is essentially unchanged; Census reports its percentage change as too small to display rather than as a number, and we report it that way rather than rounding it to zero.²

Compare that with Portland, where Multnomah County lost 20,009 while its suburbs gained, or the Bay Area, where San Francisco lost 52,471 and only outlying Contra Costa grew. San Diego is the counter-example: the dense, expensive, renter-heavy city is the part that is growing. For an owner of urban multifamily that is a materially better setup than any of those markets offer.²

The city is also the renter market. San Diego city is 47.3 percent owner-occupied, so 52.7 percent of households rent, against 45.4 percent county-wide. Median household income in the city is $108,077, slightly above the county at $106,268, and the poverty rate is 11.0 percent against 10.1 percent.²

The affordability position is mid-range by the standards of coastal California. Median gross rent countywide is $2,246, which takes about 25.4 percent of median household income on our arithmetic, well below the 35.9 percent we measured in the Bronx and above the 21 to 22 percent range across the Bay Area. Owning with a mortgage costs $3,184, a gap of $938 a month over renting, wide enough that the purchase option is not a near substitute. Median home value of $854,700 is about 8.0 times county median income.²

Supply is moderate. The county permitted 11,707 units in 2025 against 1,287,607 units of stock, about 0.91 percent. Census publishes permits and housing unit counts for the county rather than for the individual cities here, so we do not break that figure down further.²

• The county lost 16,400 residents; the city gained 21,625.
• Oceanside, on the coast, lost 2.1 percent of its population.
• The city is 52.7 percent renters, deeper than the county.
• Rent takes about 25.4 percent of income; permits run about 0.91 percent of stock.

Portland, Boston and San Francisco all show a shrinking core and a growing ring. San Diego shows the opposite, and the growing part is the renter market.

We are more constructive on San Diego than on the other California markets in this series, and the reason is demographic rather than regulatory.

We would underwrite urban San Diego, and specifically the submarkets inland of the coastal zone boundary such as North Park and the greater Hillcrest area, along with downtown and East Village. The city is growing while the county is not, it is 52.7 percent renters, rent takes a manageable 25.4 percent of income, and the $938 monthly gap between owning and renting means a rent increase does not push a tenant toward a purchase. Permitting at 0.91 percent of stock is moderate and construction employment is falling, so competing deliveries should stay contained.²¹

We would not buy in Oceanside at present. It combines the two risks in this market: a coastal location, so any redevelopment carries the replacement obligation and the eviction presumption, and a population that fell 2.1 percent. Neither alone would rule it out. Together they do.²³

On coastal assets generally we would transact, but only where the business plan does not depend on demolition or conversion. A stabilized coastal building held for income is a different proposition from a coastal building bought to be replaced, and the Mello Act does not touch the first. Any plan that involves clearing a building of its existing tenants inside the coastal zone should be underwritten with the replacement units costed in, not treated as a risk to be managed later.³

Three diligence items are specific to this market. Establish whether the parcel is inside the coastal zone, using the delineation under Division 20 of the Public Resources Code rather than a distance from the shore. Establish the income status of the existing tenants, because the obligation attaches to occupancy by low or moderate income households and applies where even one qualifying household occupies a shared unit. And obtain the eviction history for the twelve months before any application, because a substantial number of qualifying evictions in that window reverses the burden of proof onto you.³

Investors comparing California markets should read this alongside our Bay Area guide, where the binding constraint is a city's housing element status, and our Los Angeles guide, where it is rent stabilization.

A stabilized coastal building held for income is untouched by the Mello Act. A coastal building bought to be cleared and replaced is a different asset, and it should be priced as one.