Property Data APIs — Your Secret Weapon
This is one of the most important lessons in the entire course. While your competitors are manually Googling sold prices and guessing at market trends, you're going to learn how to tap directly into property data APIs — the same data sources that power the big portals and proptech companies.
An API (Application Programming Interface) is simply a way to request data from a service automatically. Think of it as a direct phone line to a database. Instead of browsing Zillow's website and manually copying numbers, you can pull the exact data you need — sold prices, rental yields, listing histories, price trends — and feed it straight into AI for analysis.
This lesson is foundational. Everything we do in Weeks 2 and 3 with market analysis, investor reports, and comparative market analysis builds on what you learn today.
What data can you actually get?
The amount of property data available through APIs is staggering. Here's what you can access:
Sold prices and transaction history — What every property on a street sold for, when it sold, and the price per square foot. In the UK, the Land Registry makes this data free and public. In the US, county records are public but APIs like Zillow and Redfin make them easy to access.
Current listings and asking prices — What's on the market right now, how long it's been listed, and any price reductions. Essential for pricing new instructions.
Rental data and yields — Current rental listings, achieved rents, and calculated yields. Gold for investor clients.
Price trends over time — How prices have moved in a postcode, suburb, or zip code over 1, 5, 10, or 20 years. Perfect for market reports.
Property details — Beds, baths, square footage, lot size, year built, property type. Useful for finding comparable properties.
Neighbourhood statistics — Demographics, crime rates, school ratings, walkability scores. Background data for area guides.
UK property data sources
HM Land Registry Price Paid Data (FREE)
This is one of the best free data sources in the world. Every residential property transaction in England and Wales since 1995 is recorded and publicly available. You can download bulk data or query specific addresses.
- What you get: Address, price paid, date of transaction, property type, new build flag, tenure
- How to access: gov.uk/government/collections/price-paid-data — bulk downloads are free. For API access, use the Land Registry's linked data API
- Best for: Comparable sales analysis, price history, market trend reports
Zoopla API
Zoopla offers property estimates, area statistics, and listing data. Their API requires developer registration.
- What you get: Zoopla valuations (Zed-Index), area averages, listing data, rental estimates
- How to access: Register at developer.zoopla.co.uk — there's a free tier for limited requests
- Best for: Quick valuations, area comparisons, rental estimates
Rightmove Data
Rightmove doesn't offer a public API, but they provide market data through their Rightmove Data Services for agents. Their monthly House Price Index is publicly available and excellent for market trend analysis.
- Best for: Market trend commentary, listing performance data (for subscribed agents)
US property data sources
Zillow API (Zillow Group)
The most widely known property data source in the US. Zillow's API provides Zestimates, listing data, and market trends.
- What you get: Zestimates (automated valuations), listing details, price history, comparable sales, neighbourhood data
- How to access: Sign up at zillow.com/howto/api/APIOverview.htm — free tier available with rate limits
- Best for: Quick valuations, comparable property searches, price history for client presentations
Redfin Data Center
Redfin publishes free market data that's among the most detailed available. Their data center provides downloadable datasets.
- What you get: Median sale prices, homes sold, inventory levels, days on market, price drops — all filterable by metro, city, zip code, and neighbourhood
- How to access: redfin.com/news/data-center — free to download, no API key needed
- Best for: Market trend analysis, seasonal patterns, inventory tracking
Realtor.com API
Provides listing data, property details, and market statistics.
- What you get: Active listings, property details, market hotness scores, price forecasts
- How to access: Developer registration at rapidapi.com — free tier available
- Best for: Active inventory analysis, market heat indicators
ATTOM Data
A premium data provider used by many proptech companies. Covers property details, tax assessments, foreclosure data, and natural hazard reports.
- What you get: Property records, tax data, deed history, foreclosure status, school data, hazard assessments
- How to access: api.gateway.attomdata.com — paid plans, but trial access available
- Best for: Deep property due diligence, investor-grade analysis
Australian property data sources
Domain API
Domain is one of Australia's two major property portals and offers a well-documented API.
- What you get: Property listings, sold data, suburb profiles, property estimates, agent information
- How to access: Register at developer.domain.com.au — free tier with limited calls, paid tiers for volume
- Best for: Listing data, suburb-level analysis, property estimates
CoreLogic
CoreLogic is the gold standard for Australian property data. It powers most of the industry's valuation and analytics tools.
- What you get: Automated valuations (AVMs), sold data, rental data, market trends, suburb analytics, property reports
- How to access: CoreLogic's API is typically accessed through subscription products like RP Data. Individual agents usually access via their agency's subscription
- Best for: Professional-grade valuations, investor reporting, comprehensive market analysis
Australian Bureau of Statistics (FREE)
ABS provides free demographic and housing data that's invaluable for area reports.
- What you get: Population data, median incomes, housing tenure patterns, growth projections
- How to access: abs.gov.au — free, downloadable datasets
- Best for: Demographic profiles for neighbourhood guides and investor reports
How to feed API data into AI
Here's where it gets powerful. Once you have property data, you feed it into ChatGPT or Claude and ask for analysis. You don't need to be a data scientist — you just paste the data and ask questions.
Getting started — your homework
You don't need to master APIs today. But here's what you should do before tomorrow's lesson:
UK agents: Go to the Land Registry Price Paid Data page (gov.uk) and download the last 12 months of data for your area. It's a CSV file. Open it in Excel or Google Sheets. You now have every property sale in your patch.
US agents: Go to Redfin's Data Center (redfin.com/news/data-center) and download the market data for your metro area. Filter by your zip codes. You now have median prices, inventory levels, and days on market — for free.
Australian agents: Go to Domain's developer portal (developer.domain.com.au) and register for a free account. Even before using the API, explore their suburb profile pages — they're packed with data you can copy and paste into AI.
Everyone: Take any five comparable sales from your area, paste them into ChatGPT or Claude, and ask: "What's the average price per square foot and what pricing trend do you see?" That's your first taste of data-driven AI analysis.