Affordable housing has a legal definition that changes by location, and it determines which programs you can enter and which landlords get tax breaks for keeping rents down.

The most common definition is that affordable rent should not exceed 30 percent of a household's gross monthly income. If you earn $3,000 a month, affordable rent in this framework is $900 or less. This 30 percent standard comes from the U.S. Department of Housing and Urban Development (HUD) and is used in most federal programs, but it is a guideline, not a law that applies everywhere.

The second layer is Area Median Income (AMI), which is what your local housing authority uses to decide who can enter affordable housing programs. AMI is the middle income in your county or metro area — half of households earn more, half earn less. A unit might be labeled "60% AMI affordable," meaning the rent is set so that someone earning 60 percent of the area median income pays no more than 30 percent of their income. In a county where AMI is $80,000, a 60% AMI unit targets households earning around $48,000 a year.

What counts as affordable in your area depends on three things: your local AMI, the income tier the program targets, and whether your state or city has added its own rules on top of federal ones.

Key Takeaways

  • Affordable housing is legally defined as rent that does not exceed 30 percent of gross household income, but the income level that qualifies varies by program and location.
  • Area Median Income (AMI) is calculated annually by county or metro area and determines the income thresholds for most affordable housing programs.
  • A unit labeled "60% AMI" means it is affordable for someone earning 60 percent of your area's median income, not 60 percent of the national median.
  • Some states and cities set their own affordability standards that are stricter than federal rules, so you need to check your local housing authority's definitions.
  • The same rent amount counts as affordable in one area and unaffordable in another, depending on local incomes.

How Area Median Income Sets the Affordability Bar

Your local housing authority publishes an AMI figure every year, usually in March or April. This number is specific to your county or metropolitan statistical area (MSA). San Francisco County's AMI is roughly $140,000; rural counties in Mississippi or West Virginia might have an AMI around $50,000. The same $1,200 rent is affordable in the second county but expensive in the first.

Programs then use percentages of AMI to set income limits. A "50% AMI" program serves households earning up to half the area median. A "80% AMI" program serves households earning up to 80 percent of the median. The rent in each tier is set so that someone at that income level pays roughly 30 percent of their income. This means a 50% AMI unit has lower rent than an 80% AMI unit in the same building, because it targets lower-income households.

You can find your area's current AMI on your local housing authority's website or through HUD's Income Limits portal. Search for your county name and the current year. The document will list income limits for different household sizes at 30%, 50%, 60%, 80%, and sometimes 120% AMI.

What the 30 Percent Rule Actually Means

The 30 percent standard applies to gross income, not take-home pay. Gross income includes wages, Social Security, disability payments, child support, unemployment benefits, and other regular money coming in before taxes. If you earn $2,000 a month gross, the affordable rent ceiling is $600, even if taxes and deductions bring your take-home to $1,500.

Some programs are stricter. A few cities and nonprofits use 25 percent as the threshold instead of 30 percent, meaning rent should not exceed one-quarter of gross income. A handful of programs for people with very low incomes use 20 percent. These are less common, but they exist, so ask the program directly what percentage they use.

The 30 percent rule is a ceiling, not a may provide. A landlord can charge less and still be considered affordable. A unit renting for $500 a month is affordable for someone earning $2,000 a month (25 percent), and it is also affordable for someone earning $3,000 a month (16.7 percent). The rule sets the maximum, not the actual price.

How States and Cities Add Their Own Rules

Federal definitions set the floor, but many states and cities have layered on additional requirements. California, for example, requires that some affordable units stay affordable for 55 years, longer than the federal 30-year minimum. New York City has its own affordability tiers that differ from HUD's standard percentages. Massachusetts counts certain utilities as part of rent for affordability calculations, while most places do not.

Some jurisdictions have created "deeply affordable" categories for households earning 30% AMI or less, recognizing that the standard 30 percent rule leaves very low-income people paying too much. Others have "workforce housing" definitions that target teachers, nurses, and other essential workers earning above the poverty line but below the area median.

Your local housing authority or city housing department publishes these local rules in their Consolidated Plan or Affordable Housing Policy. These documents are public but not always straightforward to find. Calling the housing authority directly and asking "What does affordable mean in our area?" is often faster than searching online.

How Affordability Affects Which Programs You Can Enter

Affordability definitions determine your access to specific programs. If a program targets 60% AMI households and you earn 70% AMI, you do not meet the income limit, even if the rent itself feels affordable to you. Conversely, if you earn 40% AMI and a program targets 80% AMI, you are well below the limit and may be prioritized.

Some programs have multiple tiers within one building. A mixed-income development might have units at 50% AMI, 60% AMI, and 80% AMI, with different rents for each. Your income determines which tier you can enter. This structure is common in new construction projects that receive tax credits or public funding.

Rent-controlled or rent-stabilized units in cities like New York, San Francisco, and Los Angeles have their own affordability rules that do not always align with HUD's definition. A rent-stabilized apartment might have a legal rent increase of 3 percent annually, which keeps it affordable for long-term tenants but may not match the 30 percent income standard for new residents.

What Happens When Your Income Changes

If you live in an affordable unit and your income rises above the program's limit, you may have to move or pay market rent. Some programs allow a grace period — usually one to three years — before enforcing the income limit. Others let you stay at the affordable rent as long as you remain in the unit, even if your income exceeds the limit. Rules vary by program and funding source.

If your income drops, you may become may be able to access for a lower-tier affordable unit or for additional subsidies. Some programs have waiting lists for deeper affordability levels, so report income changes to your landlord or housing authority to see what options open up.

How Affordability Definitions Affect Landlords and Developers

Landlords who participate in affordable housing programs agree to keep rents at the defined affordable level in exchange for tax credits, grants, or low-interest loans. The affordability definition determines how much revenue they can collect, which affects whether a project is financially viable. A developer building a 100-unit building at 60% AMI will have lower revenue than one building at 80% AMI, so deeper affordability requires more subsidy.

This is why many new affordable units are built at 80% AMI rather than 50% AMI — the economics work better for developers. It is also why some cities have to offer additional incentives (zoning bonuses, property tax breaks, or direct grants) to get developers to build at lower income tiers.

Frequently Asked Questions

Is the same rent affordable in every part of the country?

No. A $1,200 rent is affordable for someone earning $4,000 a month in a low-income area, but unaffordable for someone earning $3,000 a month in a high-cost city. Affordability is always relative to local income, not a fixed dollar amount. Your area's AMI determines the threshold.

What if I earn more than 80% AMI but less than 100% AMI?

You do not meet the income limit for most affordable programs. Some cities have "workforce housing" or "middle-income housing" programs that target households earning 80% to 120% AMI, but these are less common. Market-rate housing or rent information programs may be your options instead.

Can I stay in an affordable unit if my income goes up?

It depends on the program. Some allow you to stay indefinitely; others enforce the income limit after a grace period and may ask you to move or pay market rent. Ask your landlord or housing authority what the rule is for your specific unit.

Where do I find my area's current AMI?

Your local housing authority publishes it annually, usually by March or April. You can also search HUD's Income Limits portal at huduser.gov and enter your county name and year. The document lists income limits for different household sizes at various AMI percentages.

Does affordability include utilities?

Usually not in the federal definition — the 30 percent rule applies to rent only. But some states and cities count utilities as part of the affordability calculation, which lowers the rent ceiling. Check your local housing authority's rules to be sure.