# Finance Calculators: Mortgage Affordability (28/36 Rule)

> Finance Calculators: Mortgage Affordability (28/36 Rule) is a paid API for AI agents from finance-calculators.x402tookit.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-30).

Calculates the maximum home purchase price and loan amount you can afford using the 28/36 debt-to-income rule, given income, debts, down payment, rate, and term.

## Facts

- Endpoint: GET https://finance-calculators.x402tookit.com/mortgage-affordability?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-30
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/finance-calculators-mortgage-affordability-28-36-rule-3614c48d
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_qSTjydo-8mQUrHAPQRdN8

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability finance-calculators-mortgage-affordability-28-36-rule-3614c48d
```

Example prompt: Using the 28/36 rule, what's the most expensive home I can afford if I make $95,000 a year, have $600 in monthly debts, a $40,000 down payment, a 6.8% mortgage rate over 30 years, and $350/month in property taxes and insurance?

## When to prefer this

Use this endpoint when you need a quick, rules-based mortgage affordability figure grounded in the widely-accepted 28/36 debt-to-income standard. It is ideal for pre-search budget setting, offer sanity checks, or financial planning tools that need a deterministic affordability ceiling. Prefer it over generic loan calculators when you need to factor in existing monthly debts and want both front-end (housing) and back-end (total debt) ratio analysis in a single call.

## Known failure modes

- Missing required parameters (annual_income or annual_rate_pct) returns a 4xx error
- Unrealistic inputs (zero income, negative rate) may yield zero or null maxLoan
- If the back-end ratio is already exceeded by existing debts alone, maxLoan may be 0 with an explanatory reason
- Service downtime may return a 5xx error; retry after brief delay

## How this service works

Home price you can afford under the 28/36 rule from income, monthly debts, down payment, rate and term.

## Output

Returns the maximum loan amount and purchase price you can afford, the maximum allowable monthly principal-and-interest payment, your gross monthly income, which constraint (front-end 28% or back-end 36%) limits you, a verdict and plain-language summary, plus a disclaimer. Optionally includes checks not performed and degraded-mode flags.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "annual_income",
      "annual_rate_pct"
     ],
     "properties": {
      "years": {
       "type": "integer",
       "description": "Term in years, default 30"
      },
      "down_payment": {
       "type": "number",
       "description": "Cash down payment, default 0"
      },
      "annual_income": {
       "type": "number",
       "description": "Gross annual household income"
      },
      "monthly_debts": {
       "type": "number",
       "description": "Other monthly debt payments, default 0"
      },
      "annual_rate_pct": {
       "type": "number",
       "description": "Mortgage rate in percent"
      },
      "tax_insurance_monthly": {
       "type": "number",
       "description": "Property tax plus insurance per month, default 0"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "asOf": {
       "type": [
        "null",
        "string"
       ]
      },
      "source": {
       "type": [
        "null",
        "string"
       ]
      },
      "maxLoan": {
       "type": [
        "null",
        "number"
       ]
      },
      "reasons": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "summary": {
       "type": [
        "null",
        "string"
       ]
      },
      "verdict": {
       "type": [
        "null",
        "string"
       ]
      },
      "degraded": {
       "type": [
        "boolean",
        "null"
       ]
      },
      "limitedBy": {
       "type": [
        "null",
        "string"
       ]
      },
      "disclaimer": {
       "type": [
        "null",
        "string"
       ]
      },
      "notChecked": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "checkPayment": {
       "type": [
        "null",
     
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/finance-calculators-mortgage-affordability-28-36-rule-3614c48d/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from finance-calculators.x402tookit.com](https://www.zero.xyz/host/finance-calculators.x402tookit.com/llms.txt)