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 sits in the Deals tab of an Excel workbook with sale price in column B and 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 build a PMT formula for deal one
- 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
- 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 Excel workbook. It reads your deal list and calls the API Ninjas mortgage and property tax endpoints for each row, writing real figures back so the committee has defensible numbers.
Open the SheetXAI sidebar and type:
For each row in the Deals tab, 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, and writes the monthly payment. Then it calls the property tax endpoint per ZIP code and writes the rate.
What You Get
A deal workbook with two new columns ready for the committee:
- Column D: Monthly mortgage payment — calculated from the live API Ninjas 30-year fixed rate and the sale price
- Column E: Property tax rate — effective rate for that ZIP code, not a national average
The figures are defensible. They come from a live API call at a specific rate, recorded at the time of the run.
Need a total monthly cost estimate per deal? Ask SheetXAI to add mortgage plus monthly tax equivalent in a column F in the same prompt.
What If the Data Is Not Quite Ready
Deal workbooks rarely come pre-cleaned. SheetXAI handles the messiness alongside the calculation.
When sale prices have inconsistent formatting
Some are "$1,250,000," some "1250000," some "1.25M."
Normalize all sale prices in column B of the Deals tab to a numeric value. Write the normalized value back into column B, then calculate the monthly mortgage 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 of the Deals tab that have a city name instead of a ZIP code, geocode the city using API Ninjas to find the ZIP code and write it back 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 both scenarios side by side.
For each deal in the Deals tab, fetch the current 30-year and 15-year fixed rates from API Ninjas. Calculate monthly payments for both using the sale price in column B. Write the 30-year payment into column D and the 15-year payment into column E. Add 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 needs mortgage payment, tax rate, and a total cost column before noon.
Normalize sale prices in column B of the Deals tab to numeric values. For rows in column C with city names instead of ZIP codes, look up the ZIP code via API Ninjas geocoding. Calculate the monthly mortgage payment using the current 30-year fixed rate for each deal and write into column D. Look up the property tax rate per ZIP code and write into column E. Calculate a total monthly cost estimate (mortgage plus monthly tax equivalent) and write into column F. Sort the Deals tab by column F descending.
The pattern: two different API calls per row, data cleaning, and a derived calculation all in one instruction.
Try It
Get the 7-day free trial of SheetXAI and open any deal workbook, 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 in Excel or the API Ninjas in Excel overview.