App builder

Give buyers a mortgage calculator
that uses your local taxes and fees.

Describe your market and Netiva’s AI builds a public web app for payment, affordability and closing-cost estimates, with an optional lead form, a live preview and code you own.

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Starter prompt

Build a public mortgage calculator web app for a real estate team in two counties. Include three calculators: monthly payment (principal and interest, property tax, homeowners insurance, HOA dues and mortgage insurance per program — conventional below your LTV threshold, FHA on every loan, none on VA), affordability (a price range from gross monthly income, debts and cash, capped by each program’s ratio limits or by the cash left for down payment and closing costs) and closing costs (lines per county, flat or a percentage of price or loan). Store each sample rate with its checked-on date and show an estimate disclaimer under every result.

Build it in Netiva Paste the prompt into a new workspace and adjust it to your business.
Overview

Who this mortgage calculator is for

Buyers run the numbers long before they call an agent, often on a national calculator that guesses at property taxes, skips mortgage insurance and knows nothing about local transfer taxes or recording fees. The payment they settle on can fall well short of what a lender later quotes. A real estate calculator app built with Netiva puts payment, affordability and closing-cost estimates on your own site, using the tax rates, insurance figures and fee lines you keep current. Every result lists its assumptions with the date you checked them, and an optional form lets buyers ask for a call.

Key features

What your mortgage calculator can do

  • Payment breakdown line by line

    Buyers enter a price, a down payment and a loan program and see the whole monthly payment, not just principal and interest, with each part labeled and the sample rate’s date beside it.

    • Principal and interest from the standard amortization formula
    • Property tax and insurance from the county the buyer picks
    • Mortgage insurance from each program’s own rule, not a flat 20% test
    • A yearly table of balance, interest paid and the year mortgage insurance drops off

  • Affordability from income and debts

    Instead of one big number, the affordability calculator shows a price range and which of three limits caps it: the housing ratio, the total debt ratio or the buyer’s cash, each tested against the full payment.

    • Gross monthly income, monthly debts and cash for closing as inputs
    • Housing and total debt limits kept per program in the collection grid
    • A cash ceiling from the down payment plus buyer-paid closing-cost lines
    • Income and debt figures left out of your saved records

  • Closing costs by county

    Each county or town gets its own closing-cost lines — lender fees, title charges, recording fees, transfer taxes and prepaid items — marked with who usually pays, so cash to close reflects where the buyer is shopping.

    • Lines set as a flat fee or a percentage of the price or loan
    • Down payment and buyer-paid lines added into one cash-to-close figure
    • A public cost guide page for each county you serve
    • The collection assistant drafts and tidies fee lines across counties

  • Optional follow-up for buyers

    The calculators work without a sign-up. Buyers who want more can email themselves the estimate or ask for a call, and your team gets each request with the price, program and county attached.

    • An emailed copy of the estimate when the buyer asks for one
    • Call requests emailed to the agent or loan officer on duty
    • Team sign-in with saved views of open requests by status
    • A weekly email listing rates and fee lines due for a recheck
Data model

The collections behind it

Netiva keeps your records in built-in collections. Here’s a starting structure — the agent adapts it to your prompt, and you can change it any time.

Loan programs

The loan types you show, each with a dated sample rate and its own qualifying limits.

  • Name (required) Conventional 30-year fixed, FHA 30-year, VA 15-year… Text
  • Term in years (required) Number
  • Sample rate (required) Annual % you enter; shown with its checked-on date Number
  • Rate checked on (required) Date
  • Mortgage insurance rate Annual % of the loan; blank where the program charges none, such as VA Number
  • Mortgage insurance rule When it applies and ends: below 20% down to 78% LTV, FHA every loan to year 11, VA none Text
  • Housing ratio limit Highest housing payment as a % of gross income; blank where only total debt is judged Number
  • Total debt ratio limit (required) Highest monthly debts including the new housing payment, as a % of gross income Number

Areas

The counties or towns you serve, with the tax and insurance figures used in payment estimates.

  • Name (required) County or town, as buyers know it Text
  • State (required) Text
  • Property tax rate (required) Effective annual % of the purchase price — check assessment ratios, exemptions and caps Number
  • Insurance estimate (required) Typical annual homeowners premium Number
  • Figures checked on (required) Date
  • Local notes Assessment ratio, exemptions and caps, reassessment after a sale, special districts Paragraph

Closing cost lines

Each fee or charge a buyer or seller may pay at closing, set per area.

  • Line (required) Appraisal, lender’s title policy, recording fee, transfer tax… Text
  • Area Leave blank for lines that apply in every area Relation to Areas
  • Section (required) Lender fees, Title and settlement, Government fees or Prepaids Text
  • Basis (required) Flat, % of price or % of loan Text
  • Amount (required) Dollars for flat lines, a percentage otherwise Number
  • Paid by (required) Buyer, Seller or Negotiable Text
  • Checked on (required) Date

Estimate requests

Buyers who asked for a copy of their estimate or a call, with the scenario they ran.

  • Name (required) Text
  • Email (required) Text
  • Phone Needed only for call requests Text
  • Calculator (required) Payment, Affordability or Closing costs Text
  • Home price Number
  • Loan program Relation to Loan programs
  • Area Relation to Areas
  • Status (required) New, Contacted, Referred to lender or Closed Text

Required field. Types are Netiva collection field types.

Screens

Pages and screens to start with

A typical first version. Ask the agent for more, or annotate the preview to change any of them.

  • Payment calculator

    Price, down payment, program and county in; a monthly total out, split into principal and interest, tax, insurance, HOA dues and mortgage insurance.

    Public

  • Affordability

    Income, monthly debts and cash turn into a price range, with a note on which limit sets the ceiling — a ratio or the cash left after closing costs.

    Public

  • Closing costs

    Pick a county, price and program to see closing-cost lines grouped by section and a cash-to-close total, each figure shown with its checked-on date.

    Public

  • County cost guide

    One page per county you serve: its effective property tax rate and how the county assesses value, typical closing-cost lines and who usually pays each one.

    Public

  • Requests

    Copy and call requests with the scenario attached, filtered by status, calculator and county, so nobody who asked for help waits.

    Your team

  • Assumptions

    Every sample rate, tax rate and fee line with its checked-on date, sorted so the oldest figures come first.

    Your team
How it works

From prompt to a live mortgage calculator

  1. Name your calculators and market

    Tell Netiva which calculators you want, the loan programs you show and the counties you serve. The agent drafts collections for programs, areas, closing-cost lines and requests, plus the three calculator pages.

  2. Enter figures you can stand behind

    Add sample rates with dates, effective tax rates and fee lines from your title or lender partners’ current fee sheets. The collection assistant can draft lines for each county for you to check.

  3. Test against a real closing

    Run a past purchase through the live preview and compare it with that deal’s Closing Disclosure, client details removed. Annotate any result, label or disclaimer that needs work and the agent updates it.

  4. Publish and link from listings

    Publish in one click, link the calculators from your buyer and listing pages and turn on the weekly recheck email. Every change is checkpointed, so a wrong formula edit can be rolled back.

Why Netiva

Netiva vs a traditional build

Building a mortgage calculator with Netiva compared with a traditional build
Criterion With Netiva Traditional build
Updating rates and fees Your team edits rates, tax rates and fee lines in collections, each with a checked-on date A developer edits rates and fee tables hard-coded in the calculator script
Local closing costs Fee lines per county, flat or percentage-based, with who usually pays each one A generic calculator plugin with a single national closing-cost percentage
Getting started Describe what you need in chat and watch it take shape in a live preview Hire developers, or stitch together templates, plugins and a hosting plan
Content and data Built-in collections with nine field types, bound straight to your pages Set up and connect a separate database or CMS
Making changes Ask the agent; every change is checkpointed and reversible File a ticket, wait for a sprint, redeploy
Hosting and domain Global hosting and automatic SSL; connect a custom domain from the Starter plan Buy hosting, then install and renew SSL certificates yourself
Code ownership Clean production code you own and can export Locked into a template, plugin or agency setup
Examples

Ways teams use it

  • A buyer’s agent working with first-time buyers

    The agent links the affordability page in every consultation email, so the first meeting starts from a price range the buyer has already seen, and call requests arrive with the program and county the buyer tried.

  • A loan officer’s marketing team

    The team runs payment pages for conventional, FHA and VA programs with the loan officer’s NMLS ID and disclaimer under each result, and refreshes sample rates from a rate data provider it already licenses.

  • A title office serving local agents

    The office keeps a closing-cost estimator for the three counties it covers, with recording fees, transfer taxes and title charges taken from its own rate sheets, and agents link it from their listing pages.

Good to know

Before you build

  • An estimate isn’t a loan offer

    Results depend on the numbers entered. Label them as estimates, avoid words like “pre-qualified” or “approved” and send buyers to a lender: a Loan Estimate arrives within three business days of an application and is the figure to compare.

  • Payment figures in ads

    Under Regulation Z, an ad stating a payment, a down payment or a rate must also give the down payment, repayment terms and APR — which reaches any public page, these calculators included. Your sample rate is an interest rate, not an APR. Ask your broker how your state treats it.

  • Rates and fees are yours to maintain

    Netiva doesn’t supply mortgage rates, tax rates or fee schedules. Enter them from sources you trust or connect a rate data provider’s API under its license terms, then recheck them on a schedule.

  • Lender partners and referral rules

    If call requests go to a loan officer, RESPA Section 8 bars giving or taking anything of value for referring settlement business, so have co-marketing deals reviewed. Store the scenario and contact details only; income, debts and credit scores belong on the lender’s application.

Compliance note

Every figure these calculators show is an estimate built from the numbers entered — the buyer’s inputs plus the rates, tax rates and fees you maintain. It isn’t a loan offer, a pre-approval or financial or lending advice. Say so under each result on the published pages, show when your assumptions were last checked and send buyers to a licensed lender for actual terms.

FAQ

Questions about building a mortgage calculator

How does the mortgage calculator work out the monthly payment?

Principal and interest come from the standard fixed-rate amortization formula, using the loan amount, the program’s annual rate divided by 12 and the term in months. The app then adds a twelfth of the county’s annual property tax and insurance estimates, any HOA dues and mortgage insurance where the program calls for it: below your conventional threshold, on every FHA loan, never on VA. Each part is listed separately so buyers can see where the total comes from.

How does the affordability calculator decide what a buyer can afford?

It works from the debt-to-income ratio: monthly debt payments divided by gross monthly income. For each program it finds the highest price whose housing payment stays under your housing limit and, with the buyer’s other debts added, under your total debt limit. It then caps the range at the highest price whose down payment plus buyer-paid closing-cost lines fit the cash entered, and names which of the three limits bound it. Agree the limits with your lender partner.

Can the calculator show today’s mortgage rates automatically?

It can, if you have a source. Netiva apps can call REST APIs with keys stored securely, so you can ask the agent to pull each program’s sample rate from a mortgage rate data provider on a schedule. Check the provider’s license terms for public display first. Without a feed, enter a sample rate by hand; the app shows the date you checked it next to every result.

How accurate are the closing-cost estimates?

They’re only as current as the lines you enter. Each county gets its own lines, taken from your title, escrow or lender partners’ fee sheets and your area’s recording and transfer charges, and each notes who usually pays, since that depends on the contract and local custom. Treat the total as a planning figure; the buyer’s Loan Estimate and, three business days before closing, the Closing Disclosure show the actual costs.

Can the calculator handle FHA and VA loans as well as conventional ones?

Yes. Each program is its own record with a term, sample rate, mortgage insurance rate and the rule for when that insurance applies and ends, so FHA, VA and conventional sit side by side. VA charges no monthly mortgage insurance; FHA charges annual MIP on every loan whatever the down payment. You can also ask the agent to add an upfront charge financed into the loan, such as FHA’s upfront premium or the VA funding fee. Take current figures from your lender partner.

Can I add the mortgage calculator to the website I already have?

Netiva publishes the calculators as their own web app, so you can link to them from your current site’s buyer pages, listing pages and emails. To serve them from an address such as calculators.yourteam.com, add the DNS records Netiva lists at your registrar; custom domains need the Starter plan or higher. Compare the current plans on Netiva’s pricing page before you publish.

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Drafted with AI assistance from Netiva’s product pages and reviewed by the Netiva team. Example data models, screens and prompts are illustrative starting points, not customer projects.

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