Thanks, that's really nice to hear. Happy to share:

- Listings: RentCast's API (licensed), pulled weekly.

- Parcel boundaries: state and county GIS services where they publish statewide parcels (about 20 states), and Realie (licensed) for the rest.

- Public land: USGS PAD-US 4.1, filtered to fee-owned, open-access land of 50+ acres.

- Elevation: USGS 3DEP point queries. Roads: Census TIGER. Flood: FEMA's National Flood Hazard Layer. Wildfire: Forest Service Wildfire Hazard Potential (2023). ZIP search: Census ZCTA centroids.

The free state parcel services were the biggest hunt: every state publishes differently, and a couple that looked open turned out to be test or internal-use-only endpoints.