What public records can and cannot tell you
County and state governments publish an enormous amount of parcel data for free: boundaries, parcel identifiers, assessed characteristics, sometimes year built and lot size. The US Census Bureau publishes a geocoder that resolves an address to coordinates and to state and county FIPS codes.
None of it is a substitute for what you observe. Assessment records are frequently stale, characteristics are often self-reported, and permit history is incomplete in most jurisdictions. Public data is a head start, not a finding.
Provenance is the whole discipline
Any value you carry into a report should be able to answer three questions: which dataset produced it, when it was retrieved, and how confident the match is. A value without those three attributes should not appear in a client document.
Handle conflicts explicitly
When a county GIS service and a state open-data portal disagree about year built, the correct behavior is to show both and let a human decide. Silently choosing the newer or the higher-confidence source hides a real disagreement from the person who signs the report.
Never let prefill overwrite observation
The safe rule is one-directional: public data may populate an empty field, and only after an explicit human acceptance. It may never replace something an inspector entered from the site.
Label preliminary output as preliminary
Setback screening, buildable-area estimates and overlay flags derived from public layers are preliminary reference information. They are not permit approvals, zoning determinations or flood determinations, and reports should say so plainly.