A mid-sized developer we know budgets zero dollars for pre-acquisition data. Not because he is cheap. Because he has built his pre-acquisition process around sources that are free to the public and reliable enough to stake a purchase decision on. The data that matters in the first 48 hours of a deal is mostly free, if you know which doors to open.
Here is the stack.
FEMA Map Service Center
The Map Service Center hosts every effective Flood Insurance Rate Map in the United States. Type an address, get a FIRMette, save the PDF. It is the authoritative source for flood zone status and Base Flood Elevation.
Two pitfalls. First, the effective map may be older than the preliminary map currently under review in the same community. Always check the community's status page for pending map actions. Second, the MSC interface is cumbersome. For programmatic access, FEMA's National Flood Hazard Layer is a WMS or REST endpoint that returns zone polygons directly.
USDA Web Soil Survey
The Web Soil Survey is the successor to the paper county soil surveys that sat on every county engineer's shelf. It returns soil map units for any defined area of interest, with hydrologic soil group, drainage class, septic suitability, and building suitability ratings.
For a pre-acquisition screen, the three pieces to extract are the hydrologic soil group, the depth to water table, and any hydric soil inclusions. Hydric soils are a wetland indicator and a red flag for Army Corps jurisdiction.
The Web Soil Survey is free, public, and programmatically accessible through NRCS's Soil Data Access service.
USGS National Map and StreamStats
USGS hosts a pile of free datasets. The two most useful for civil work are the National Map and StreamStats.
The National Map serves topography at various resolutions. For parcel-scale work, 3DEP one-meter DEM is the current standard. A DEM-based slope analysis identifies constrained terrain, potential drainage patterns, and the rough cut-fill profile before a surveyor sets foot on site.
StreamStats returns drainage basin delineations and flow statistics for any point. A developer concerned about downstream drainage impacts or upstream capture can run a StreamStats pour point in two minutes.
Both are free.
State DOT portals
Every state DOT publishes route centerlines, access class designations, and some level of traffic count data. Coverage varies wildly. FDOT's access management maps are comprehensive. Caltrans publishes traffic counts back decades. Some smaller state DOTs publish only a PDF of the route log.
For a site with frontage on a state-maintained road, the access class is a first-order constraint. Access classes control whether direct driveways are permitted, the required spacing of driveways, and whether a traffic impact study is triggered. This is the kind of information that should enter the decision before the offer, not after.
County GIS and property appraiser sites
Almost every US county publishes a GIS parcel viewer. The coverage is uneven in quality, but in aggregate the public parcel layer is the most valuable single dataset in real estate due diligence.
What to pull: current ownership, legal description, recorded easements, zoning overlay, flood overlay, any special tax district, and recent sales history. On more sophisticated counties, you can also pull assessed value, building footprint geometry, and permit history. In Florida, the property appraiser's site is usually more detailed than the county GIS. In Texas, the appraisal districts, not the counties, are the authoritative source.
Municode, AmLegal, and the long tail
For jurisdictions on Municode or AmLegal, the municipal code is available as a searchable tree. Specific dimensional standards, permitted uses, and overlay regulations are a few clicks away.
For jurisdictions on neither, there is a longer walk. Many cities and counties publish their code as a PDF on the municipal website. Many do not publish it at all, requiring a records request or an in-person visit to the clerk's office. This is the friction point where the free-data strategy starts to break down.
State environmental databases
Several states maintain structured environmental databases that matter for acquisitions. The New Jersey DEP's GeoWeb is one of the best. Massachusetts's MassGIS is another. California's CalEPA EnviroStor is the public record for contaminated sites.
The federal equivalents are EPA's Envirofacts, the CERCLIS database for Superfund sites, and the RCRA Info database for hazardous waste sites. For any acquisition, a five-minute check of these three federal databases is the cheapest Phase I preliminary screen you will ever run.
What free data cannot do
Free data cannot do title work. It cannot do geotechnical. It cannot do traffic engineering. It cannot do a Phase I environmental site assessment, though it can inform one. It cannot do a survey.
It can, however, answer most of the yes-or-no questions that drive the decision to proceed or walk. Is this in a flood zone. What is the zoning. Are there wetlands. Is the access constrained. Is there a known contamination event on record.
Answer those questions before writing a letter of intent. The professional scopes of work fit around them. The deal that clears those checks is the deal worth paying for a survey on.
Where AI fits in
The stack above has existed for a decade. What has not existed is a way to query it in natural language from a single interface. That is the part AI adds. Not new data. A faster and more literate way to consume data that was already free.
The best developers we work with run this stack daily. The tool that makes them faster is additive to the stack, not a replacement for it.