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API Keys Reference — prei

This reference documents the API keys required to power the data-driven intelligence features of prei, including signup links and usage details.

Keys At-A-Glance

Environment Variable Service Free Tier Signup URL
ATTOM_API_KEY ATTOM Data 1,000 calls/mo api.attomdata.com
CENSUS_API_KEY US Census Bureau Unlimited api.census.gov
BLS_API_KEY Bureau of Labor Statistics 25,000 calls/day data.bls.gov/registrationEngine
RENTCAST_API_KEY RentCast 50 calls/mo rentcast.io
GREATSCHOOLS_API_KEY GreatSchools Free basic tier greatschools.org/api
WALKSCORE_API_KEY Walk Score Free basic tier walkscore.com/professional/api

1. ATTOM Data API Key (ATTOM_API_KEY)

Used for property-level detail enrichment, foreclosures, taxes, and comps valuation.

  • Purpose: Enriches a newly created property page with structural details (sqft, bedrooms, bathrooms, year built) and fetches local comparable sales (comps) for BRRRR After-Repair Value (ARV) calculations.
  • Get Key: Go to api.attomdata.com, click "Sign Up", create a developer account, and copy your API key from the dashboard.
  • Cost / Limits: The Free Trial includes 1,000 requests per month.
  • Budget Monitoring:
  • ATTOM_MONTHLY_BUDGET=1000.00
  • ATTOM_COST_PER_CALL=0.01
  • Configure these in .env to prevent unexpected charges.

2. Census API Key (CENSUS_API_KEY)

Used for population growth and demographic tracking at the ZIP-code level.

  • Purpose: Powers the Markets page population signal. Calculates population growth over the last 1, 3, and 5 years.
  • Get Key: Visit api.census.gov/data/key_signup.html, fill out the form, and you will receive your API key via email.
  • Cost / Limits: 100% Free with no daily limit.

3. Bureau of Labor Statistics API Key (BLS_API_KEY)

Used for state/metro unemployment rates and employment diversity index.

  • Purpose: Powers the Markets page economic scoring signals. Pulls monthly Local Area Unemployment Statistics (LAUS) and Quarterly Census of Employment and Wages (QCEW).
  • Get Key: Register at data.bls.gov/registrationEngine/ to receive your registration key.
  • Cost / Limits: Free tier allows up to 25,000 requests per day.

4. RentCast API Key (RENTCAST_API_KEY)

Used for gross rent estimates and rental comps.

  • Purpose: Provides expected rental estimates for properties and BRRRR deals based on active/historical rental listings in the immediate radius.
  • Get Key: Register at rentcast.io or go directly to the developer dashboard.
  • Cost / Limits: Free tier includes 50 requests per month.

5. GreatSchools API Key (GREATSCHOOLS_API_KEY)

Used for neighborhood school quality indicators.

  • Purpose: Displays local school ratings on the Property detail scorecard and factors into the neighborhood rating signal.
  • Get Key: Apply at greatschools.org/api.
  • Cost / Limits: Free basic tier for non-commercial or personal developer use.

6. Walk Score API Key (WALKSCORE_API_KEY)

Used for walkability and transit quality scores.

  • Purpose: Pulls Walk Score, Transit Score, and Bike Score for the property address to display on the scorecard dashboard.
  • Get Key: Apply at walkscore.com/professional/api.
  • Cost / Limits: Free basic tier.

Safe Environment Management

Local (.env)

Never commit your actual API keys to git. Put them in your root .env file (copied from .env.example), which is already in .gitignore.

# Example .env config
ATTOM_API_KEY=your_key_here
CENSUS_API_KEY=your_key_here
BLS_API_KEY=your_key_here

Dev Container / Codespaces

If you are using Codespaces, do not edit .devcontainer/devcontainer.json to insert real keys. Instead: 1. Open GitHub → Repo Settings → Secrets and Variables → Codespaces 2. Add your keys as Codespace secrets (e.g. ATTOM_API_KEY) 3. Rebuild your Codespace — the variables are automatically injected into your terminal and devcontainer.json environment.

Render (render.yaml or Dashboard)

When deploying to production: 1. Open Render Dashboard → Your Web Service → Environment 2. Add the corresponding environment variables as hidden/secret variables. 3. Re-deploy. Do not hardcode them in render.yaml.