What Is Affordable Housing?

Affordable housing is housing a household can pay for while still covering its other basic needs. In the United States, the standard yardstick is simple: a home is considered affordable when rent or mortgage payments plus utilities take no more than 30% of a household’s gross income. By that measure, whether a home is “affordable” depends as much on who lives there as on what it costs.

The phrase is also used in a second, narrower way. When a city council, developer, or reporter talks about “building affordable housing,” they usually mean homes set aside for households below a specific income limit, tied to a percentage of the local area median income. Those homes are usually paid for in part by public programs and bound by legal rent limits. This guide explains both meanings, who affordable housing serves, how it differs from public housing, and what it actually looks like.

The 30% Rule: How Affordability Is Measured

The 30% rule is the closest thing the United States has to an official definition of affordability. Federal housing policy generally treats housing as affordable if it costs no more than 30% of household income. Households that pay more are considered cost-burdened, and households that pay more than half their income are severely cost-burdened. HUD uses the same thresholds in its CHAS data, the custom Census tabulations that local governments use for housing planning.

Where the 30% figure came from

The ratio has deep roots. According to the Congressional Research Service (CRS), it grew out of a rule of thumb from the late 1800s and early 1900s, “a week’s wages for a month’s rent.” Federal agencies later adopted a cost-to-income ratio for housing assistance. The landmark step was the Brooke Amendment to the Housing and Urban Development Act of 1969, which capped public housing rents at 25% of a resident’s income. Laws passed in 1981 and 1983 raised that share to 30% across federal rental assistance programs. It has stayed there since.

What counts as housing costs

For renters, the calculation uses gross rent: the contract rent plus utilities such as electricity, gas, and water. For homeowners, it includes mortgage payments, property taxes, insurance, and utilities. Income is measured before taxes.

Suppose a household earns $48,000 a year, or $4,000 a month. Thirty percent of that is $1,200.

The limits of the rule

The 30% standard is popular because it is easy to calculate and lets researchers compare places and years. CRS notes several weaknesses:

• It ignores choices and trade-offs. A renter who pays 32% to live near work counts as burdened, while one who pays 29% but faces a long, expensive commute does not.
• It treats all incomes the same. Spending 30% on housing leaves a high earner plenty for other needs. It may leave a low-income family with too little for food, child care, and medical bills.
• It skips other costs. Transportation, child care, and health care vary widely from family to family.

Some researchers therefore prefer a residual income approach. It subtracts the actual cost of other necessities from income and asks whether what remains can cover housing. It is more realistic, but harder to calculate, and methods vary.

Affordable to Whom? Income Bands and AMI

Because a $1,500 rent is a bargain in some regions and out of reach in others, affordable housing programs define eligibility relative to local incomes. HUD publishes income limits each year for every metro area and non-metro county, based on area median income (AMI). The FY 2026 limits took effect on May 1, 2026. Federal law, in the United States Housing Act, sets the core categories.

All of these limits are adjusted for household size, so a family of four can earn more than a single person and still qualify. The exact dollar figures differ in every area. To find them, use HUD’s income limits lookup on the HUD User website rather than relying on national averages. For a step-by-step walkthrough, see who qualifies for affordable housing.

Households in the moderate-income band are the focus of workforce housing. They often earn too much for traditional subsidies but too little to afford market rents near their jobs. The guide on affordable housing vs. workforce housing explains where the two overlap.

Two Kinds of Affordable Housing

Subsidized, income-restricted housing

Subsidized housing receives public money or tax benefits in exchange for keeping rents within reach of lower-income households. The rules are usually written into a regulatory agreement or deed restriction that runs with the property for decades. Tenants must certify that their income is under the limit when they move in.

The biggest source of new subsidized rental housing is the Low-Income Housing Tax Credit (LIHTC). CRS describes it as the federal government’s primary tool for developing and rehabilitating affordable rental housing. HUD’s database lists about 3.9 million tax-credit units placed in service from 1987 through 2024. Starting in 2026, Public Law 119-21 permanently increased the amount of credits each state can allocate every year by 12%. Other sources include federal rental assistance, state and local housing trust funds, and grants.

Naturally occurring affordable housing

Naturally occurring affordable housing, often called NOAH, is privately owned housing with rents that happen to be low, with no subsidy or legal restriction. It is typically older, plainer apartment buildings and single-family rentals. The National League of Cities describes NOAH as the most common form of affordable housing in the country.

Because NOAH has no rent restrictions, it can disappear when a building is sold, renovated, or caught up in a rising market. Keeping it affordable is a major focus of preservation work.

How Affordable Housing Differs From Public Housing

People often use “affordable housing” and “public housing” interchangeably. They are not the same.

Public housing is one specific program, created by the Housing Act of 1937. Local public housing agencies own and operate the buildings with federal funding. Residents generally pay the highest of 30% of their adjusted monthly income, 10% of their gross monthly income, or a designated welfare housing payment. The federal subsidy covers the rest of the operating cost.

HUD groups its rental assistance into three categories: public housing, tenant-based assistance, and privately owned, project-based assistance. Tenant-based help, now the Housing Choice Voucher Program, is the most common. A voucher lets a family rent a private apartment and pay roughly 30% of its income, with the voucher covering the rest up to a limit. Project-based rental assistance attaches a similar subsidy to particular privately owned buildings.

Tax-credit housing works differently. A LIHTC apartment has a fixed maximum rent: by law, gross rent cannot exceed 30% of the income limit that applies to the unit. Rent does not adjust to each tenant’s actual income. Suppose a unit’s rent is set at the maximum for a household at 60% of AMI, and the family living there earns 40% of AMI. That family would pay about 45% of its income in rent. This is one reason some tax-credit residents also use a voucher or other rental assistance.

For the full history and current state of the program, see public housing in America.

Who Affordable Housing Serves

Affordable housing serves a wide range of households. Residents include seniors on fixed incomes, people with disabilities, families with children, and working adults in lower-wage jobs such as retail, food service, home health care, and child care.

The need far exceeds the supply. In its March 2026 report The Gap, which analyzes 2024 Census data, the National Low Income Housing Coalition (NLIHC) estimated:

• About 11 million renter households had extremely low incomes, nearly a quarter of all renters.
• The country was short 7.2 million rental homes that were affordable and available to them.
• There were only 35 affordable and available homes for every 100 extremely low-income renter households.

The same report notes that housing assistance programs reach only about one in four eligible households. Vouchers are not an entitlement: funding is limited, and applicants are usually placed on a waitlist. CRS notes that the wait can range from several months to many years.

Cost burdens also reach well up the income ladder. CRS estimated that in 2023, 22.6 million renter households (49.5%) and 20.3 million homeowner households (23.6%) were cost-burdened. More than a quarter of renter households (26.5%) were severely cost-burdened. For the wider picture, see the housing affordability crisis.

What Affordable Housing Looks Like

Modern income-restricted housing often looks no different from its market-rate neighbors. Common forms include:

• Garden-style and mid-rise apartments, the typical tax-credit property
• Senior apartment buildings with age and income restrictions
• Townhomes and small multifamily buildings that fit into existing neighborhoods
• Mixed-income housing, where restricted and market-rate units share one building
• Permanent supportive housing, which pairs an apartment with services for people leaving homelessness
• Ownership homes kept affordable through a community land trust or shared-equity model
• Smaller homes, such as accessory dwellings, cottage clusters, and manufactured homes, which can cost less to build and buy

Together, these options form a housing continuum that runs from emergency shelter through subsidized rentals to market-rate ownership. Our guide to the housing continuum explains how the pieces connect.

The Bottom Line

Affordable housing has two meanings. In general, it is any home that costs no more than 30% of a household’s income. In policy, it is housing reserved for households below set percentages of area median income, usually with public support behind it. It includes public housing, voucher-assisted apartments, tax-credit buildings, and a large stock of unsubsidized older homes with modest rents. Knowing which meaning someone intends, and which income band they have in mind, is the first step in any conversation about housing affordability.