The Scenario
You are a real estate analyst at a private equity firm. Thursday at noon, the investment committee meets to review 150 property deals sourced this quarter. Each deal has a sale price in column B and a ZIP code in column C. The committee wants monthly mortgage payment and effective property tax rate alongside every deal before they will approve moving any to the next stage.
The bad version of this week:
- You google the current 30-year fixed rate
- You manually calculate the monthly payment for deal one using a formula you write from scratch
- You find a property tax tool online, enter the first ZIP code, copy the rate
- You realize you have 149 rows left and it is already Wednesday afternoon
- You paste in a rough national average for the remaining rows and hope no one asks about it
- Two committee members ask about ZIP code 30076 specifically and you have a national average where a real rate should be.
The precise version is one prompt.
The Easy Way: One Prompt in SheetXAI
SheetXAI is an AI agent inside your spreadsheet. It reads your deal list and calls the API Ninjas mortgage and property tax endpoints for each row, writing the results back so the committee has real figures for every deal.
Open the SheetXAI sidebar and type:
For each row, calculate the monthly mortgage payment using the sale price in column B and the current 30-year fixed rate from API Ninjas, then write the result to column D. Then look up the effective property tax rate for each ZIP code in column C using API Ninjas and write the rate percentage into column E.
SheetXAI fetches the current 30-year rate from API Ninjas, applies it to each sale price using the standard mortgage formula, and writes the monthly payment. Then it calls the property tax endpoint per ZIP code and writes the rate. Two API calls per row, one prompt.
What You Get
A deal sheet with two new columns ready for the committee:
- Column D: Monthly mortgage payment — calculated from the current API Ninjas 30-year fixed rate and the sale price in column B
- Column E: Property tax rate — effective rate for the ZIP code, not a national average
The figures are defensible. They come from a live API call at a specific rate, not a rough estimate or a formula that uses last month's rate.
Need a total-cost-of-ownership estimate per deal, mortgage plus tax plus insurance? Ask SheetXAI to add that calculation in the same prompt.
What If the Data Is Not Quite Ready
Deal sheets rarely come pre-cleaned. SheetXAI handles the messiness alongside the calculation.
When sale prices have inconsistent formatting
Some are formatted as "$1,250,000," some as "1250000," some as "1.25M."
Normalize all sale prices in column B to a numeric value before calculating mortgage payments. Write the normalized value into column B, then calculate the monthly payment using the current 30-year rate from API Ninjas and write into column D.
When some ZIP codes are missing
A few rows have the city name in column C but no ZIP code.
For rows in column C that have a city name instead of a ZIP code, geocode the city using API Ninjas to find the ZIP code and write it into column C. Then look up the property tax rate for all rows and write into column E.
When you want to compare 30-year versus 15-year payments
The committee wants to see both scenarios side by side.
For each deal, fetch the current 30-year and 15-year fixed rates from API Ninjas. Calculate monthly payments for both terms using the sale price in column B. Write the 30-year payment into column D and the 15-year payment into column E. Add a column F showing the monthly difference.
When the full pre-committee run is one prompt
Raw deal list, inconsistent price formats, some missing ZIP codes, and the committee wants mortgage payment, tax rate, and a total monthly cost column ready before noon.
Normalize sale prices in column B to numeric values. For rows in column C with city names instead of ZIP codes, look up the ZIP code via geocoding in API Ninjas. Calculate the monthly mortgage payment using the current 30-year fixed rate from API Ninjas for each deal and write into column D. Look up the property tax rate per ZIP code and write into column E. Then calculate a total monthly cost estimate (mortgage + monthly tax equivalent) and write into column F. Sort the sheet by column F descending.
The pattern: data cleaning, two different API calls per row, and a derived calculation all in one instruction.
Try It
Get the 7-day free trial of SheetXAI and open any property deal sheet, then ask SheetXAI to add mortgage payments and property tax rates using API Ninjas. The API Ninjas integration is included in every SheetXAI plan. See also how to bulk-enrich a ticker list with market data or the API Ninjas in Google Sheets overview.