OpenChainGraph Suite · ART-770

Total Cost of Homeownership

The mortgage payment is usually less than two thirds of what a house actually costs. This node ports Apex #153 (AL-167): it amortizes the loan month by month, grows each recurring cost year by year, and returns the gross and net cost of ownership over the hold, a break-even monthly rent, and a cost-composition breakdown. Every rate is user-supplied; nothing is fetched.

HousingPITI + CompositionDeterministicZero PIIClient-side only

🔒 All inputs are processed locally in your browser. No data is transmitted. Do not enter real personal data; use synthetic or anonymised inputs only.

Scope & reliance

Deterministic port of Apex #153: standard amortization, MI while post-payment LTV is strictly above the drop threshold (default 80%, Homeowners Protection Act borrower-cancellation leg; the 78% automatic-termination leg is not modeled), property tax on purchase price grown yearly, insurance/maintenance/HOA/utilities grown yearly, opportunity cost as annual compounding of cash at close, deduction benefit (interest + SALT-capped property tax) × marginal rate. The SALT-cap default shown ($10,000) is the Apex fallback; the official 2026 figure is $40,400 (26 USC 164(b)(7)). Enter marginal rate 0 if you take the standard deduction (2026 single $16,100). No clock is read: the computation is deterministic and zkVM-promotable. The 1%-maintenance panel value is display-only; the maintenance % input below drives the math.

Purchase & loan

price (USD)

max 50000000

downPct (%)

below 20 starts LTV above 80%, so MI accrues

annualRate (% APR)

user-supplied; nothing is fetched

termYears (years)

1–40; months capped at 480

closingPct (% of price)

miRatePct (% of original loan / yr)

charged while LTV strictly above the drop threshold

Recurring costs

propertyTaxRate (% / yr)

insuranceAnnual (USD / yr)

hoaMonthly (USD / mo)

maintenancePct (% / yr)

this input drives the math (1% rule-of-thumb default)

extraUtilities (USD / yr)

Growth, timeline & tax

appreciationPct (% / yr)

may be negative

taxGrowthPct (% / yr)

inflationPct (% / yr)

holdYears (years, integer)

minimum 1

sellingPct (% of sale)

clamped 0–20

oppRatePct (% / yr)

marginalRatePct (%)

0 if you take the standard deduction

cMiDropLTVPct (%)

Homeowners Protection Act cancellation leg

cSaltCap (USD / yr)

Apex fallback; official 2026: $40,400

Result

Cost composition

Proof status

This node ships compute_proof_ready: deferred: no zkVM receipt exists for art-770. The result above is recomputable from the same inputs via compute(pp) in chaingraph/kernels/art-770-total-cost-of-homeownership.kernel.mjs.

Execution Hash & §4 Artifact

SHA-256 execution hash (canonical JSON of policy_parameters + output_payload):

Run the AINumbers MCP tool `total_cost_of_homeownership`. Task: Total cost of homeownership ported from ApexLogics Apex #153 (AL-167): month-by-month mortgage amortization, MI while post-payment LTV is strictly above a drop threshold, year-grown property tax, insurance, maintenance, HOA and utilities, an interest-plus-SALT deduction offset, opportunity cost on cash at close, and gross/net cost of ownership with break-even monthly rent and a bps cost composition. Call it with arguments: {"policy_parameters":{"price":450000,"downPct":20,"annualRate":6.5,"termYears":30,"closingPct":2.5,"miRatePct":0.55,"propertyTaxRate":1.1,"insuranceAnnual":1800,"hoaMonthly":0,"maintenancePct":1,"extraUtilities":1200,"appreciationPct":3,"taxGrowthPct":2,"inflationPct":3,"holdYears":7,"sellingPct":6,"oppRatePct":5,"marginalRatePct":0,"cMiDropLTVPct":80,"cSaltCap":10000}} Verify before trusting: call `verify_execution_hash` on mcp.ainumbers.co (https://mcp.ainumbers.co/mcp) with the parameter `claimed_hash` set to the returned `execution_hash`, passing the full artifact the run returned (the object containing `policy_parameters` + `output_payload` + `execution_hash`; equivalently `policy_parameters` + `output_payload` with `claimed_hash`), not the bare hash string. Return the ledger link https://ledger.ainumbers.co/ so a human can re-verify without contacting us. PII rule: All inputs are processed locally in your browser. No data is transmitted. Do not enter real personal data — use synthetic or anonymised inputs only. Over MCP, the run happens on the AINumbers worker. No AINumbers server stores your inputs. Open the tool with the sample prefilled: https://ainumbers.co/chaingraph/art-770-total-cost-of-homeownership.html#p=v1.H4sIAAAAAAAA_wFeAaH-eyJwcmljZSI6NDUwMDAwLCJkb3duUGN0IjoyMCwiYW5udWFsUmF0ZSI6Ni41LCJ0ZXJtWWVhcnMiOjMwLCJjbG9zaW5nUGN0IjoyLjUsIm1pUmF0ZVBjdCI6MC41NSwicHJvcGVydHlUYXhSYXRlIjoxLjEsImluc3VyYW5jZUFubnVhbCI6MTgwMCwiaG9hTW9udGhseSI6MCwibWFpbnRlbmFuY2VQY3QiOjEsImV4dHJhVXRpbGl0aWVzIjoxMjAwLCJhcHByZWNpYXRpb25QY3QiOjMsInRheEdyb3d0aFBjdCI6MiwiaW5mbGF0aW9uUGN0IjozLCJob2xkWWVhcnMiOjcsInNlbGxpbmdQY3QiOjYsIm9wcFJhdGVQY3QiOjUsIm1hcmdpbmFsUmF0ZVBjdCI6MCwiY01pRHJvcExUVlBjdCI6ODAsImNTYWx0Q2FwIjoxMDAwMH3BY1LwXgEAAA

Total Cost of Homeownership

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