ZIP 21740 is both a Zillow ZIP market identifier and a Census ZCTA match; a ZCTA is a statistical area, not identical to a USPS delivery ZIP. The immediate decision question is how a current blended asking-rent signal should be read against household financial, stock, and bedroom-standard evidence that measures different things. In June 2026, Zillow’s ZORI is $1,317 per month, up 3.29% year over year. ZORI is a typical observed asking-rent index blended across rental types, so it establishes a ZIP-wide current benchmark rather than the price, utility package, or availability of a named property. The useful distinction here is between that current market signal and records that describe surveyed occupied homes or administrative program standards.
Stock evidence precedes any availability conclusion. In the ACS 2024 five-year matched ZCTA, the housing inventory totals 27,339 units: 25,276 are occupied and 2,063 are vacant, a 7.5% overall vacancy rate. The structure mix records 19,683 single-family units and 1,276 in the large-multifamily category. Vacancy composition separately lists 479 vacant-for-rent units, 298 vacant-for-sale units, and 231 seasonal units. These are area-level category counts, not a listing feed; the overall rate includes all vacancy reasons, and the for-rent count does not establish that a particular home is currently obtainable, at the ZIP benchmark, or suitable for a particular household.
The financial lens is also confined to the matched ZCTA survey universe. It records 11,290 renter-occupied homes, representing 44.7% of occupied homes, and median household income of $62,873. It records 5,325 renter households spending 30% or more of income on gross rent, an observed burden share of 47.2%. A cross-source arithmetic comparison annualizing the current ZIP index produces a 25.1% asking-rent-to-median-income comparison. A household would need $52,680 in annual income for the current index to equal 30% of income. That required-income screen is arithmetic, not advice, a claim about applicant qualification, or evidence of what any renter pays at a given unit.
Zillow, ACS, and HUD should be read as parallel, not merged, rent universes. The ACS median gross rent is $1,080; it is a five-year survey statistic for occupied renter homes and includes selected utilities. The current ZORI is 21.9% above that median, but the values should not be merged because Zillow measures a current typical observed asking-rent index across rental types. The local FY2026 HUD FMR/SAFMR two-bedroom standard is $1,233, and the ZIP ZORI is 6.8% higher. HUD FMR/SAFMR is an administrative bedroom-specific standard, not asking rent, so it is a calibration input and a separate program benchmark rather than a second market quote.
Bedroom interpretation uses HUD ratios rather than observations of ZIP listings. Scaling the ZIP ZORI through the local HUD ladder produces modelled monthly estimates of $908 for a studio, $1,026 for one bedroom, $1,317 for two bedrooms, $1,816 for three bedrooms, and $2,031 for four bedrooms. The underlying HUD standards are $850, $961, $1,233, $1,700, and $1,901 in the same bedroom order. The two-bedroom model matches the ZIP index by construction. These are modelled estimates, never measured bedroom rents: they translate a ZIP-wide blended index using the local HUD ladder and cannot show a unit’s actual layout, condition, utility treatment, or advertised rent.
Context values situate, but do not redefine, the ZIP signal. The City of Hagerstown context has a $1,442 rent measure and a 56.7% renter share; Washington County context has a $1,444 rent measure and a 33.2% renter share; and the Hagerstown-Martinsburg, MD-WV metro context has a $1,601 rent measure and a 24.4% rent-to-income measure. Each rent context measure is above the ZIP ZORI, while tenure and income-ratio comparisons refer to their named wider scopes. City, county, and metro statistics are contextual only; they cannot be pooled with ZIP/ZCTA results or used to assign the profile of an individual property.
Limits determine the final read: Zillow’s blended current index lacks lease-specific terms; ACS is a ZCTA survey rather than a USPS delivery geography; and HUD is an administrative standard. At the property level, check the actual advertised monthly base rent, bedroom count and floor plan, whether selected utilities are included, all recurring and nonrecurring charges, lease term, availability date, occupancy requirements, and whether the address is within the relevant ZIP delivery area. Confirm how the advertised rent is defined and which listed charges recur throughout the lease. Those checks identify the offered terms without assuming that a ZIP index, a survey burden, a vacancy count, or a modelled estimate describes that unit directly.
","findings":[{"body":"Zillow identifies a current ZIP-level asking-rent signal, whereas ACS reports the gross-rent experience of occupied renter homes across a survey period. Selected utilities belong in the ACS measure, not necessarily the advertised asking rent. The gap therefore helps identify which benchmark is being used; it does not authorize a direct substitution, an error claim, or a unit-level rent conclusion.","title":"Market index and survey rent serve different decisions"},{"body":"Each bedroom figure is generated by applying relative values from the local HUD ladder to the ZIP-wide Zillow index. This makes the sequence useful for consistent size comparison, including the fact that the anchor size aligns mechanically with the index. It does not create observed ZIP listings, measured bedroom medians, or evidence that any available home follows the modelled spread.","title":"The bedroom series is a scaling exercise"},{"body":"The income comparison annualizes the current index against the area median, while the burden statistic records an ACS survey distribution among renter households. The required-income calculation simply solves a specified rent-share equation. Neither metric tests a household’s actual income, credit, lease terms, utility obligations, or eligibility, and neither establishes the cost burden associated with a particular property.","title":"Income and burden describe different tests"},{"body":"Overall vacancy includes several reasons a housing unit is unoccupied, while the for-rent category is a survey classification rather than an active inventory. Structure counts describe the area’s stock, not its current advertised mix. A prospective property analysis therefore still needs direct confirmation of availability, charges, bedroom configuration, and what is included in the quoted rent.","title":"Vacancy counts are not availability"}],"risks":["Zillow’s ZIP index is not a contemporaneous quote for a specific available home. A listing can differ because the index blends rental types, while lease terms and utility treatment are property-specific.","The ACS ZCTA survey does not map perfectly to USPS delivery ZIP boundaries, and its occupied-home, multi-year survey coverage can differ from the current listings represented by Zillow.","HUD standards are administrative bedroom-specific benchmarks. Applying their ladder to Zillow produces a consistent modelled sequence, but it cannot establish measured rents, actual layouts, condition, or lease pricing.","Vacancy and cost-burden records are aggregate evidence, not proof about any individual unit. They cannot confirm availability, affordability, included charges, tenant eligibility, or the terms of a proposed lease."],"qa":[{"a":"Zillow tracks a typical observed asking-rent index at the ZIP level and across a blended set of rental types. ACS summarizes gross rent reported for occupied renter homes during a five-year survey and includes selected utilities. Different timing, coverage, and rent concepts mean the measures should be compared as separate benchmarks, not added or treated as interchangeable.","q":"Why is Zillow different from ACS gross rent?"},{"a":"No. The bedroom series takes the single ZIP index and applies ratios from the HUD bedroom ladder. It is explicitly a modelled estimate, anchored mechanically at the reference bedroom size. Because it is not a listing survey or transaction dataset, it cannot report a measured bedroom rent, current availability, property condition, or an individual lease price.","q":"Are the bedroom estimates actual advertised rents?"},{"a":"The required-income figure divides annualized monthly rent by the specified share of income. It is a transparent arithmetic screen for comparing a rent benchmark with income, nothing more. It does not account for other debts, household composition, subsidies, deposits, utilities, credit, or a landlord’s application criteria, so it is not qualification advice or an approval test.","q":"How should the required-income figure be used?"},{"a":"Confirm the advertised base rent, bedroom count, floor plan, utility inclusions, recurring and nonrecurring charges, lease length, availability timing, and address geography. Also determine whether the quoted price is for the exact unit under review. These checks connect an individual offering to its actual terms without assuming that ZIP index, vacancy, burden, or model values describe it.","q":"What needs verification at the property level?"}],"sources":[{"key":"apartment_list_time_on_market","name":"Apartment List Time on Market — listing liquidity","release":"Apartment List 2026-07","pulledAt":"2026-08-08","url":"https://www.apartmentlist.com/research/category/data-rent-estimates"},{"key":"apartment_list_vacancy","name":"Apartment List Vacancy Index — rental vacancy","release":"Apartment List 2026-07","pulledAt":"2026-08-08","url":"https://www.apartmentlist.com/research/apartment-list-vacancy-index-methodology"},{"key":"census_zcta_facts","name":"Census ACS five-year — ZCTA housing and income","release":"ACS 2024 5-year ZCTA","pulledAt":"2026-08-08","url":"https://api.census.gov/data/2024/acs/acs5.html"},{"key":"hud_zip","name":"HUD USPS crosswalk and Small Area FMRs — ZIP rent fallback","release":"ZIP-CBSA 2025Q4 + SAFMR 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