Methodology
Sources & data status
Every number the calculators start from, where it comes from, and when someone last checked it. Generated from the same files the math reads, so it can't quietly fall out of sync.
The honest summary
The calculators start from 49 editable defaults: 2 set by law, 2 from official data, 4 from market surveys, 8 market conventions, and 33 our own estimates. Only 5 link to a specific source document, and only 1 has a recorded re-verification date so far. The rest say "not yet re-verified" below rather than show a date we can't back up.
Every default is editable on its calculator. If a value is marked our estimate, it's a placeholder for your real number, not a fact about your building or lender.
- Law or regulation Set by statute or regulation. Changes only when the law does.
- Official data Published by a government agency or Freddie Mac.
- Market survey From broker or industry reports. Typical, not universal.
- Market convention How NYC landlords, lenders, or boards usually operate. Not a law; yours may differ.
- Our estimate A reasonable midpoint we picked so the calculators have a starting value. Replace it with your real number.
Mortgage defaults
| Assumption | Default | Basis | Source | Last verified |
|---|---|---|---|---|
| 30-year fixed mortgage rateConventional, conforming, 20% down, excellent credit. Bankrate showed 6.97% the same week. Jumbo loans and lender overlays can differ materially.Used on: Co-op, Condo | 6.95% | Official data | Freddie Mac Primary Mortgage Market Survey ↗As of Sep 17, 2026 | Sep 23, 2026 |
| Loan termUsed on: Co-op, Condo | 30 years | Market convention | None: site estimate | Not yet re-verified |
Co-op purchase defaults
| Assumption | Default | Basis | Source | Last verified |
|---|---|---|---|---|
| Co-op down paymentMinimum for most buildings. Mid-range Manhattan boards often require 25%; luxury buildings 30 to 50%.Used on: Co-op | 20% | Market survey | Skybriz; Prevu (2025) (cited by name) | Not yet re-verified |
| Co-op board max debt-to-incomeLong-standing NYC board standard. Outer-borough buildings may allow 30 to 35%; some Park/Fifth Ave buildings cap at 20 to 25%.Used on: Co-op | 28% | Market convention | Prevu; YRE (2025) (cited by name) | Not yet re-verified |
| Co-op post-closing liquidityMonths of mortgage + maintenance. Conservative/luxury boards require 24+. Retirement accounts are generally excluded.Used on: Co-op | 12 months | Market convention | Prevu; Aaron & Geoff (Compass), 2026 (cited by name) | Not yet re-verified |
| Co-op monthly maintenanceMid-range citywide estimate. Rough medians: Queens ~$750, Brooklyn ~$900, Manhattan ~$1,500 to $1,800.Used on: Co-op | $1,200/mo | Our estimate | Elliman / Miller Samuel (Q4 2024) (cited by name) | Not yet re-verified |
| Buyer attorney (co-op)NYC range $2,500 to $5,000.Used on: Co-op | $4,000 | Market survey | Prevu; Brick Underground (2025) (cited by name) | Not yet re-verified |
| Bank attorney (co-op)Used on: Co-op | $1,500 | Our estimate | None: site estimate | Not yet re-verified |
| Co-op application / board feeUsed on: Co-op | $750 | Our estimate | None: site estimate | Not yet re-verified |
| Move-in deposit (refundable)Refundable, but it is still cash you need on closing day.Used on: Co-op | $1,000 | Our estimate | None: site estimate | Not yet re-verified |
| Other fixed costs (UCC filing, lien search, etc.)Used on: Co-op | $800 | Our estimate | None: site estimate | Not yet re-verified |
| Co-op variable closing costs (loan origination)Excludes mansion tax (calculated separately) and any buyer-side flip tax.Used on: Co-op | 0.5% | Our estimate | None: site estimate | Not yet re-verified |
Condo purchase defaults
| Assumption | Default | Basis | Source | Last verified |
|---|---|---|---|---|
| Condo down paymentConventional conforming baseline. Jumbo lenders often require 25 to 30%.Used on: Condo | 20% | Market convention | None: site estimate | Not yet re-verified |
| Lender max back-end debt-to-incomeSome lenders target 36%; compensating factors can allow higher.Used on: Condo | 43% | Official data | CFPB / Fannie Mae (qualified mortgage guidance) ↗ | Not yet re-verified |
| Condo common chargesManhattan full-service often $1,500 to $3,000+; Brooklyn/Queens boutique often $500 to $900.Used on: Condo | $1,000/mo | Our estimate | None: site estimate | Not yet re-verified |
| Condo property taxReported citywide average is ~$15,134/yr ($1,261/mo); the default rounds to $1,250. Abatements change this dramatically.Used on: Condo | $1,250/mo | Market survey | Habitat Magazine / NYC DOF 2025-26 tentative assessment roll (cited by name) | Not yet re-verified |
| HO-6 insuranceUsed on: Condo | $75/mo | Our estimate | None: site estimate | Not yet re-verified |
| Buyer attorney (condo)Used on: Condo | $5,000 | Our estimate | None: site estimate | Not yet re-verified |
| Lender feesUsed on: Condo | $3,500 | Our estimate | None: site estimate | Not yet re-verified |
| AppraisalUsed on: Condo | $1,000 | Our estimate | None: site estimate | Not yet re-verified |
| Recording feesUsed on: Condo | $750 | Our estimate | None: site estimate | Not yet re-verified |
| Building / managing agent feesUsed on: Condo | $1,500 | Our estimate | None: site estimate | Not yet re-verified |
| Owner's title insurance (% of price)Mid-range NYC resale condo estimate; varies by insurer and endorsements.Used on: Condo | 0.45% | Our estimate | None: site estimate | Not yet re-verified |
| Lender's title policy (% of loan)Used on: Condo | 0.1% | Our estimate | None: site estimate | Not yet re-verified |
| Condo reserve buffer (when enabled)Off by default: condos do not impose co-op-style board reserves, but lenders or buyers may want a buffer.Used on: Condo | 6 months | Our estimate | None: site estimate | Not yet re-verified |
| Working capital contribution (months of common charges, when enabled)Common in new development; off by default.Used on: Condo | 2 months | Our estimate | None: site estimate | Not yet re-verified |
Renting defaults
| Assumption | Default | Basis | Source | Last verified |
|---|---|---|---|---|
| Landlord income requirement (x monthly rent)NYC market convention, not a law. Some landlords use 35x or 45x.Used on: Rent | 40× | Market convention | None: site estimate | Not yet re-verified |
| Guarantor income requirement (x monthly rent)Used on: Rent | 80× | Market convention | None: site estimate | Not yet re-verified |
| Max rent-plus-debt to income (when DTI screening is on)30 to 35% is typical for buildings that screen on DTI. Off by default.Used on: Rent | 35% | Market convention | None: site estimate | Not yet re-verified |
| Security depositHSTPA caps security deposits at one month for most NYC rentals. The default is the cap.Used on: Rent | 1 month | Law or regulation | NYC HPD (Housing Stability and Tenant Protection Act of 2019) ↗As of Jun 14, 2019 | Not yet re-verified |
| Application feeHSTPA caps background/credit check fees at $20. The default is the cap.Used on: Rent | $20 | Law or regulation | NYC HPD (Housing Stability and Tenant Protection Act of 2019) ↗As of Jun 14, 2019 | Not yet re-verified |
| Building / move-in admin feeMove-in deposit, key deposit, elevator reservation, etc.Used on: Rent | $500 | Our estimate | None: site estimate | Not yet re-verified |
| Utility setupCon Ed deposit, internet install, etc.Used on: Rent | $250 | Our estimate | None: site estimate | Not yet re-verified |
| Renter's insuranceNYC average roughly $15 to $25/month.Used on: Rent | $15/mo | Market survey | ValuePenguin ↗ | Not yet re-verified |
| Renter reserve bufferMonths of rent + insurance + debts kept in savings after move-in.Used on: Rent | 2 months | Our estimate | None: site estimate | Not yet re-verified |
Moving defaults
| Assumption | Default | Basis | Source | Last verified |
|---|---|---|---|---|
| Movers (local NYC move)A placeholder for a small local move. Walk-ups, distance, volume, and weekends move it a lot; get a quote. | $1,500 | Our estimate | None: site estimate | Not yet re-verified |
| Boxes and moving supplies | $150 | Our estimate | None: site estimate | Not yet re-verified |
| Guarantor company fee (% of one month's rent, per lease year)Our guarantor-companies guide reports fees commonly around 60% to 110% of a month's rent depending on credit and income. Off by default on /cost-to-move/; this is the value used when you turn it on. | 70% | Our estimate | None: site estimate | Not yet re-verified |
Selling defaults
| Assumption | Default | Basis | Source | Last verified |
|---|---|---|---|---|
| Seller broker commissionTypical NYC range is 4% to 6% of sale price, negotiable.Used on: Sell | 5% | Market convention | None: site estimate | Not yet re-verified |
| Seller attorney feeRoughly $1,500 to $3,000 for a straightforward resale.Used on: Sell | $2,500 | Our estimate | None: site estimate | Not yet re-verified |
| Seller title and miscellaneous closing costsPayoff/satisfaction fee, move-out deposit, filing fees.Used on: Sell | $1,000 | Our estimate | None: site estimate | Not yet re-verified |
| Co-op flip tax (seller)Set by each building's proprietary lease; commonly 1% to 3%, some buildings charge none.Used on: Sell | 2% | Our estimate | None: site estimate | Not yet re-verified |
| Co-op transfer / processing fee (seller)Used on: Sell | $500 | Our estimate | None: site estimate | Not yet re-verified |
Long-run projections defaults
| Assumption | Default | Basis | Source | Last verified |
|---|---|---|---|---|
| Yield on savings while you save to buyA placeholder, not a rate quote. High-yield savings and money-market rates move with Fed policy; enter your own account's APY on the savings planner. | 3% | Our estimate | None: site estimate | Not yet re-verified |
| Annual rent increaseFree-market NYC rents have swung from double-digit drops (2020) to double-digit jumps (2022). Rent-stabilized renewals follow the Rent Guidelines Board instead. | 3% | Our estimate | None: site estimate | Not yet re-verified |
| Annual home price changeA placeholder, not a forecast. Co-op prices in many NYC submarkets were flat for most of the 2010s. | 3% | Our estimate | None: site estimate | Not yet re-verified |
| Annual increase in maintenance / common charges, taxes and insurance | 3% | Our estimate | None: site estimate | Not yet re-verified |
| In-unit repairs and upkeep (per year, % of home value)The building's charges cover the structure and common areas; the inside of the unit (appliances, floors, paint) is on you. Lower than the house rule of thumb (1%) for that reason. | 0.5% | Our estimate | None: site estimate | Not yet re-verified |
| Annual return on money not tied up in the homeAfter-tax, after-inflation is not implied; this is a nominal placeholder. Use what you would actually earn on the down payment if you kept renting. | 5% | Our estimate | None: site estimate | Not yet re-verified |
Tax tables, income limits, and rate tiers
These are applied by the calculators rather than edited directly. Each is covered by automated tests that pin its thresholds.
| Table | Basis | Source | Last verified |
|---|---|---|---|
| Federal income tax brackets, standard deduction, FICA wage baseTax year 2026Used on: Required Salary Calculator, /salary/ | Law or regulation | IRS (Rev. Proc. 2025-32 and 2026 COLA notices) ↗ | Sep 17, 2026 |
| New York State income tax bracketsTax year 2026 (FY2026 budget rate cut)Used on: Required Salary Calculator, /salary/ | Law or regulation | NYS Dept. of Taxation and Finance (NYS-50-T-NYS) ↗ | Sep 23, 2026 |
| NYC resident income tax bracketsTax year 2026 (fixed thresholds, unchanged for many years)Used on: Required Salary Calculator, /salary/ | Law or regulation | NYS Dept. of Taxation and Finance (IT-201 instructions) (cited by name) | Sep 17, 2026 |
| NYC Area Median Income, 100% AMI by household size (1-8)2026. Checked against HPD's published 2026 chart on 2026-10-03; the earlier table was about 22% lower than HPD's figures.Used on: NYC Affordable Housing Calculator, NYC Housing Reality Check | Official data | NYC HPD, 2026 New York City Area AMI chart (HUD-derived) ↗ | Oct 3, 2026 |
| Mansion tax tiers ($1M to $25M+, whole-price, not marginal)1% base tier; NYC supplemental tiers above $2M since July 1, 2019Used on: NYC Co-op Affordability, NYC Condo Affordability, /buy/, Compare All Options, NYC Housing Reality Check | Law or regulation | NYS Dept. of Taxation and Finance (Publication 1099) ↗ | Not yet re-verified |
| Mortgage recording tax (borrower share: 1.80% under a $500K loan, 1.925% at $500K+)Current NYC/NYS rates. Applies to condos and houses, not co-ops (co-op loans are personal property).Used on: NYC Condo Affordability, /buy/, Compare All Options, NYC Housing Reality Check | Law or regulation | NYC Dept. of Finance ↗ | Not yet re-verified |
| NYC Real Property Transfer Tax (1.00% up to $500K, 1.425% above)Current NYC ratesUsed on: NYC Sale Net Proceeds Calculator | Law or regulation | NYC Dept. of Finance ↗ | Not yet re-verified |
| NYS transfer tax (0.4%, plus the 0.25% additional base tax on NYC residential sales of $3M+)Additional base tax in effect since July 1, 2019. Attribution of the 0.25% as a state tax (not a city tax) was corrected on 2026-10-02.Used on: NYC Sale Net Proceeds Calculator | Law or regulation | NYS Dept. of Taxation and Finance (TSB-M-19(1)R; Tax Law §1402) ↗ | Not yet re-verified |
| PMI rate tiers by down payment (0.52% to 1.20% of the loan per year below 20% down)Typical conventional pricing, ~720-740 creditUsed on: NYC Co-op Affordability, NYC Condo Affordability, Compare All Options, NYC Housing Reality Check, /buy/ | Market survey | Urban Institute; MGIC and Radian published rate cards (cited by name) | Not yet re-verified |
Market data
Median rents and sale prices are cited, not calculated, and each keeps its own as-of date, because the best sources publish on different schedules.
- Citywide median rent: $3,995/mo, March 2026, StreetEasy Market Reports ↗
- Citywide median co-op price: $505,917, Q1 2025, StreetEasy / Baruch College (Zicklin School) NYC Housing Market Trends ↗
- Citywide median condo price: Not yet tracked. We haven't found a stable, dated citywide source.
Neighborhood figures are cited on each neighborhood page, with the broker zone they actually cover and their own dates. See the Affordability Index for how the citywide snapshot is updated.
Spot something out of date?
Tell us on the contact page or open an issue on GitHub ↗. Each value lives in src/data/assumptions.ts or src/data/sourceTables.ts, and a test fails if a calculator's default disagrees with it. See how the math works for the rest.