Monthly Payment API

How it works

1. On page load, call GET /v1/{brand}/options to get the two customer questions (labels + dropdown values).
2. With the customer’s answers plus the structure’s delivery ZIP and total price, call POST /v1/{brand}/estimate.
3. Show what comes back. Eligibility, terms, payments, APRs, Apply links and disclosure text are all pre-computed.

Your widget, your layout

You decide when to call the API and how to show the results. No button is required. The test page lets you try three styles:

• A · Automatic: call /estimate whenever an input or the price changes, and show the payments without a button.
• B · Term dropdown: show one payment and let the customer switch terms from a dropdown (start on loans.defaultTermYears).
• C · Button + tiles: the customer presses a button, then picks a term tile.

For automatic updates, only call the API once the ZIP has 5 digits, price is above 0 and both questions are answered. Wait about 0.4 seconds after the last keystroke, and ignore any older response that comes back after a newer one. That keeps it fast and well under the limit of 120 rent-to-own quotes per visitor every 10 minutes. Switching terms needs no new call, because every term is already in the response.

Try A · Try B · Try C

1 · GET /v1/stoltzfus/options

Build your two <select>s from questions.creditScore.options and questions.ownProperty.options, then send the value back.

{
  "questions": {
    "creditScore": { "label": "What is your credit score?", "placeholder": "— Select credit score —",
      "options": [ { "value": "840", "label": "840 – 850" }, … { "value": "500", "label": "Below 550" } ] },
    "ownProperty": { "label": "Do you own the property where the project is located?",
      "options": [ { "value": "own", "label": "Yes, I own the property" },
                   { "value": "biz", "label": "Yes, my business owns the property" },
                   { "value": "no",  "label": "No, I do not own the property" } ] }
  },
  "lenders": { "upgrade": { "minCreditScore": 680, "minAmount": 2000, "maxAmount": 100000, … }, "thrive": { … }, "rto": { … } },
  "disclosures": { … }, "displayRules": [ … ]
}

2 · POST /v1/stoltzfus/estimate

GET /v1/stoltzfus/estimate?zip=19310&price=16820&creditScore=720&ownProperty=own also works, which is handy for testing in a browser tab.

const res = await fetch('https://payment-estimate-api.pages.dev/v1/stoltzfus/estimate', {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({ zip: '19310', price: 16820, creditScore: '720', ownProperty: 'own' })
});
if (res.status === 503) { /* hide the payment section — estimates temporarily off */ }
const data = await res.json();

Response (shortened)

{
  "ok": true,
  "input": { "zip": "19310", "state": "PA", "price": 16820, "creditScore": "720", "ownProperty": "own" },
  "loans": {
    "available": true,
    "defaultTermYears": 20,                     // pre-select this term (the longest)
    "terms": [                                  // ONE payment per term — use these for your payment choices
      { "years": 5, "label": "5-Year", "monthlyPaymentDisplay": "$372", "aprDisplay": "7.99% APR*", "footnote": "†",
        "paymentNote": "Months 1–6 are interest-only; …", "bestLender": "thrive",
        "offers": [ { "lenderName": "Thrive Financial", "monthlyPaymentDisplay": "$372", "aprDisplay": "7.99% APR*", "applyLink": "…" },
                    { "lenderName": "Upgrade", "monthlyPaymentDisplay": "$349", "aprDisplay": "8.99% APR*", "applyLink": "…" } ] },
      …
      { "years": 20, "label": "20-Year", "monthlyPaymentDisplay": "$164", "aprDisplay": "9.99% APR*", "footnote": "†", "offers": [ … Thrive only … ] }
    ],
    "byLender": {                               // full per-lender detail, exactly as the estimator shows it
      "upgrade": { "eligible": true, "terms": [ 5, 7, 10, 12, 15-year … ] },
      "thrive":  { "eligible": true, "terms": [ … incl. interestOnlyPayments for months 1–6 … ] }
    },
    "message": null                             // text to show when available = false
  },
  "rentToOwn": {
    "available": true, "creditCheck": false, "defaultTermMonths": 48,
    "terms": [ { "months": 24, "monthlyPaymentDisplay": "$1,048.77", "upfrontPayment": 3364 }, … ],
    "overMaxText": null,                        // set when the price is over $25,000 (payments are for $25,000)
    "notes": [ "Rent-to-own is not available for 2-story structures or …" ],
    "applyLink": "https://payment-estimate-api.pages.dev/v1/stoltzfus/apply/rto",
    "reason": null, "reasonText": null          // why it’s unavailable, when available = false
  },
  "disclosures": {
    "forThisWidget": [                          // show ALL of these, in order — word-for-word from our estimator
      { "type": "paragraph", "paragraphs": [ { "text": "Stoltzfus Structures is not a lender…", "html": "…" } ] },
      { "type": "heading", "text": "Important Disclosures" },
      { "type": "section", "id": "disc-rto", "title": "Rent-to-Own (SmartPay)",
        "paragraphs": [ { "text": "You do not own the structure until…", "html": "… higher than the cash price …" } ] },
      …
    ],
    "all": [ … ],                               // the estimator's whole footer, incl. products this widget doesn't offer
    "representativeExample": "…", "rentToOwnStructures": "Structures that are 2 stories or … do not qualify for rent-to-own."
  },
  "displayRules": [ … ]
}

Errors return HTTP 400 with {"ok":false,"error":"invalid_input","fields":{"zip":"Enter a valid 5-digit US ZIP code"}}. The messages are written for customers, so you can show them as-is.

Display rules (please follow)

• Always show a loan payment together with its APR and term. Never show a payment by itself.
• Keep the * on APRs and the † on interest-only terms, and put the matching disclosures on the page.
• Don’t name the lender on the payment choices. Show lender names only at the Apply step (terms[].offers).
• No APR or interest rate for rent-to-own. It’s a lease, not a loan.
• When a result has overMaxText, show it next to those payments.
• Disclosures: render every block in disclosures.forThisWidget, in order. Use html to keep the bold text. They are copied word-for-word from our estimator and update automatically when we change them, so please don’t retype or edit them.
• Show each lender’s applyHint (the small print under our Apply buttons) next to its Apply button.
• Don’t call any of these products “unsecured”.

Do / don’t (what compliant looks like)

Errors and “not available” reasons

Every error is JSON {"ok":false,"error":…}. The simulator values work on /estimate as a query parameter or a "simulate" field in the POST body, and are never counted in usage stats.

Developer kit

Everything is ready to use. Copy the three widget files into the Next.js project, or build your own UI from the types.

Launch checklist

1. Open the test page, press Run all scenarios, and confirm all pass.
2. Add the widget to a garage page on staging or localhost (localhost is already allowed). Send Tim any other staging address to allow.
3. Feed it the total price from your price calculator, including options. Don’t call the API for custom-quote structures (Build On-Site, Attached); show “request a quote”.
4. Check each widget style you use with the test page’s Error simulator: 503, 400 and rent-to-own down.
5. Confirm Apply buttons use applyLink and open in a new tab only when applyOpensNewTab is true.
6. Confirm the disclosures from disclosures.forThisWidget appear on the page, word for word.
7. Phone check: the widget fits a 360-pixel-wide screen.
8. Send Tim the staging link for a compliance look before going live.
9. Go live. Tim gets an automatic email if our rules change or estimates switch off, and so do you once you’re on the alert list.

Usage stats and alerts

The API keeps anonymous counts only (estimates shown, Apply clicks per lender, per day). It never stores customer answers, ZIPs or prices. Apply clicks are counted when buttons use applyLink, which forwards the customer to the lender. A monitor checks every hour and emails if our estimator’s rates, rules or disclosures change (the API already follows them, so your widget needs no change) or if estimates switch off.

Field reference

Questions

Tim Brazil, Lending Manager. Rates and rules are maintained on our side. When a lender changes terms, our estimator is updated, and this API and your widget pick up the change automatically.