For ZIP 78666 in San Marcos, TX, the decision question is how to read a current typical asking-rent benchmark alongside bedroom sizing, household measures, and housing-stock composition—not as a quote for a particular home. Zillow’s June 2026 ZIP-level ZORI is $1,395 per month, down 2.13% year over year. This is a typical observed asking-rent index blended across rental types, so it is a market reference rather than a unit-specific advertised price. The five-digit label is both a Zillow ZIP market identifier and a matched Census ZCTA; a ZCTA is a statistical area and is not identical to a USPS delivery ZIP. That geographic distinction matters because statistical reporting and delivery boundaries are not the same thing.
The bedroom pattern translates the ZIP index into relative size tiers. The modelled monthly ZIP estimates for a studio, one, two, three, and four bedrooms are $1,103, $1,178, $1,395, $1,772, and $2,074, respectively. These values scale ZIP ZORI using the local HUD ladder; they are modelled estimates, never measured bedroom rents. The local FY2026 HUD standards put a two-bedroom benchmark at $1,480 and a four-bedroom benchmark at $2,200. HUD FMR/SAFMR is an administrative bedroom-specific standard, not asking rent. Accordingly, the two-bedroom model matches the ZIP index by construction, while the steps between bedroom sizes reflect the HUD ladder rather than observed bedroom-specific listings.
Income and renter-burden measures describe the matched ACS 2024 five-year ZCTA survey rather than current applicants. Median household income is $54,737, with a $3,230 margin of error. Annual income associated with paying the ZIP index at 30% of income is $55,800. This 30% required-income screen is arithmetic, not advice or an applicant qualification rule. Renter-occupied homes account for 61.9% of occupied housing, and the ACS estimate shows 12,445 renter households spending 30% or more of income on gross rent, equal to 59.2% of renter households. These are aggregate household measures; they do not establish a particular renter’s income, expenses, or eligibility for a specific property.
Housing stock supplies a separate view of the setting in which asking rents are observed. The ZCTA has 36,580 housing units and a 7.2% vacancy rate. Of vacant units, 1,108 are classified as for rent, while 224 are for sale and 57 are seasonal. The structure mix includes 15,816 single-family units and 8,360 large-multifamily units. These categories describe survey-period housing inventory and broad structure types, not current condition, lease status, price, or availability at any individual address. In particular, a unit counted vacant for rent is not proof that it is presently advertised, ready to occupy, or priced near the ZIP index.
The rent measures require separate interpretation rather than a blended conclusion. Zillow ZORI is the ZIP-level typical observed asking-rent index. ACS median gross rent is $1,319, with a $39 margin of error; it is a five-year survey measure of occupied renter homes and includes selected utilities. The ACS figure is 5.8% below the Zillow index, but that numerical difference does not create a like-for-like asking-rent gap because the universes, timing, occupancy basis, and utility treatment differ. As a separate arithmetic comparison, the $1,395 ZIP index equals 94.3% of the local two-bedroom HUD standard. That comparison does not convert HUD FMR/SAFMR into a market asking-rent observation.
Wider geography provides context without replacing the ZIP evidence. The City of San Marcos context has $1,408.31 rent and a 69.2% renter share; the Hays County context has $1,571 rent and a 35.9% renter share; and the Austin-Round Rock-Georgetown, TX metro context has $1,653 rent and 9.5% apartment vacancy. Each is a city, county, or metro scope rather than the ZIP market identifier or matched ZCTA. The differences show that wider-area rent, tenure, and apartment-vacancy measures operate at broader geographic scopes, with their own definitions, and should be treated as context rather than as substitutes for the ZIP-level ZORI or ZCTA survey estimates.
Important limits remain at the property level. ZORI does not supply a quoted rent, bedroom count, utility bill, concession, availability date, or lease term for a particular unit. ACS carries sampling uncertainty and describes occupied renter homes, while HUD standards are administrative benchmarks and the ZCTA is not an exact USPS delivery ZIP. A property-level review would need the advertised rent, confirmed bedroom designation, lease duration, included and separately billed utilities, recurring fees, deposits, availability status, and the property’s stated screening terms. Neither aggregate vacancy nor observed renter burden can prove the affordability, vacancy, or suitability of any particular unit.