Worked Example — Jumbo Conventional Purchase (30-Year Fixed)

A Jumbo 30-year fixed purchase for a $2,500,000 home in Miami, FL with a $2,000,000 loan amount. Jumbo loans exceed the conforming loan limit and are funded by private lenders rather than Fannie Mae or Freddie Mac.

What is a Jumbo Loan?
Jumbo loans are non-conforming mortgages exceeding the FHFA conforming loan limit ($766,550 for most areas in 2024). Lenders hold them in portfolio and apply stricter underwriting: typically 12+ months PITI reserves, 10–20% minimum down, and no PMI on most products. The API detects jumbo automatically from the loan amount — loan_type remains "Conventional".

Scenario Parameters

Parameter	Value
Loan Purpose	Purchase
Loan Type	Conventional (Jumbo — non-conforming)
List Price	$2,500,000
Loan Amount	$2,000,000
Down Payment	$500,000 (20%)
LTV	80%
Credit Score	780
State / City / ZIP	FL / Miami / 33130
Monthly Income	$17,500
Lock Period	30 days
Loan Term	30 years
loid	44
Loan Officer ID (loid)	6309

Request Payload

Use loan_type: "Conventional" — the engine identifies jumbo automatically from loan_amount exceeding the conforming limit for the county.

POST https://api.bankingbridge.com/rateflow
Content-Type: application/json
x-api-key: uL6aLuwfcq1dUvEZTq3Gv2O0KgorNbYXXXXXXXX

{
  "lock_period": 30,
  "first_time_homebuyer": false,
  "loan_type": "Conventional",
  "list_price": 2500000,
  "loan_purpose": "purchase",
  "loan_amount": 2000000,
  "credit_score": 780,
  "state": "FL",
  "city": "Miami",
  "zipcode": "33130",
  "coords": { "lat": 0, "lng": 0 },
  "residency_type": "primary_home",
  "property_type": "single_family_home",
  "cash_out": 0,
  "down_payment": 500000,
  "waive_escrows": false,
  "monthly_income": 17500,
  "loan_term": "30",
  "loid": 6309,
  "id": 44,
  "withCredentials": false,
  "min_credit": 780,
  "aus": "NotSpecified"
}

cURL Example

curl -X POST "https://api.bankingbridge.com/rateflow" \
  -H "x-api-key: uL6aLuwfcq1dUvEZTq3Gv2O0KgorNbYXXXXXXXX" \
  -H "Content-Type: application/json" \
  -d '{
    "lock_period": 30,
    "first_time_homebuyer": false,
    "loan_type": "Conventional",
    "list_price": 2500000,
    "loan_purpose": "purchase",
    "loan_amount": 2000000,
    "credit_score": 780,
    "state": "FL",
    "city": "Miami",
    "zipcode": "33130",
    "residency_type": "primary_home",
    "property_type": "single_family_home",
    "cash_out": 0,
    "down_payment": 500000,
    "monthly_income": 17500,
    "loan_term": "30",
    "loid": 6309,
    "id": 44,
    "min_credit": 780,
    "aus": "NotSpecified"
  }'

JavaScript (fetch) Example

const response = await fetch("https://api.bankingbridge.com/rateflow", {
  method: "POST",
  headers: {
    "Content-Type": "application/json",
    "x-api-key": "uL6aLuwfcq1dUvEZTq3Gv2O0KgorNbYXXXXXXXX"
  },
  body: JSON.stringify({
    lock_period: 30,
    first_time_homebuyer: false,
    loan_type: "Conventional",
    list_price: 2500000,
    loan_purpose: "purchase",
    loan_amount: 2000000,
    credit_score: 780,
    state: "FL",
    city: "Miami",
    zipcode: "33130",
    residency_type: "primary_home",
    property_type: "single_family_home",
    cash_out: 0,
    down_payment: 500000,
    monthly_income: 17500,
    loan_term: "30",
    loid: 6309,
    id: 44,
    min_credit: 780,
    aus: "NotSpecified"
  })
});
const data = await response.json();
console.log(data.pricing_results);

Python (requests) Example

import requests

headers = {
  "Content-Type": "application/json",
  "x-api-key": "uL6aLuwfcq1dUvEZTq3Gv2O0KgorNbYXXXXXXXX"
}

payload = {
  "lock_period": 30,
  "first_time_homebuyer": False,
  "loan_type": "Conventional",
  "list_price": 2500000,
  "loan_purpose": "purchase",
  "loan_amount": 2000000,
  "credit_score": 780,
  "state": "FL",
  "city": "Miami",
  "zipcode": "33130",
  "residency_type": "primary_home",
  "property_type": "single_family_home",
  "cash_out": 0,
  "down_payment": 500000,
  "monthly_income": 17500,
  "loan_term": "30",
  "loid": 6309,
  "id": 44,
  "min_credit": 780,
  "aus": "NotSpecified"
}

response = requests.post(
  "https://api.bankingbridge.com/rateflow",
  json=payload,
  headers=headers
)
data = response.json()

Sample Response Structure

At exactly 80% LTV, pmi_monthly is 0. Expect 3–8 jumbo lenders depending on your configured Rateflow lender set.

{
  "returncode": 0,
  "status": "success",
  "loid": 44,
  "pricing_results": [
    {
      "lender_name": "Example Jumbo Lender A",
      "program_name": "Jumbo 30-Year Fixed",
      "rate": 7.125,
      "apr": 7.248,
      "points": 0.00,
      "monthly_payment": 13477.62,
      "pmi_monthly": 0
    },
    {
      "lender_name": "Example Jumbo Lender B",
      "program_name": "Jumbo 30-Year Fixed",
      "rate": 7.000,
      "apr": 7.312,
      "points": 0.875,
      "monthly_payment": 13306.07,
      "pmi_monthly": 0
    }
  ]
}

Jumbo Key Notes:

• No special flag needed: The engine identifies jumbo from loan_amount exceeding the conforming limit.
• No PMI at 80% LTV: pmi_monthly is 0. Jumbo lenders typically require 20%+ down to avoid portfolio risk surcharges.
• Jumbo rates price independently from conforming MBS markets — spreads vs. conforming vary by lender.
• $17,500/month income (~$13,477 P&I) = ~77% front-end DTI. Jumbo lenders typically want ≤43% DTI and 12 months PITI in verified reserves.