Methodology
This is the whole pipeline, in plain English, including its limits. We'd rather over-explain the boring parts than let you assume a model is doing work that a one-line field check is actually doing. If you can't tell which part is a dumb rule and which part is a model, you can't tell which part to trust — so here's the line, drawn explicitly.
The three layers
Rules cut the list (not AI)
Six deterministic filters reduce ~900–1,000 parcels to a workable shortlist. String matches, numeric thresholds, a blocklist lookup. Reproducible: the same list gives the same answer every time. Auditable: every dropped parcel records exactly one reason.
AI does the analyst layer
Two jobs — research (find and validate the sale, confirm where the list lives this year, catch a county that moved its auction platform, gather the context around each parcel) and per-parcel reasoning (turn raw flags into a short, readable read with a specific next step and sources). It reads, cross-checks, and explains. It does not generate the structural signals and it does not reach a verdict.
You decide (irreducibly human)
The output is "worth a closer look" or "probably skip, here's why" — never "bid," never a number. The decision depends on your capital, risk tolerance, and local knowledge.
The six filters in plain English
- 1. No situs address (paper lots)
- Drops any parcel printed with no street address. These are un-developable legacy subdivision lots, and this single check does the large majority of the reduction.
- 2. Minimum bid out of range
- Drops parcels below a floor (trivially small openers, often paper lots that slipped past the address check) and above a ceiling (properties that warrant a dedicated research project, not a shortlist row). On Riverside: $10,000 floor, $300,000 ceiling.
- 3. Zip blacklist (low-liquidity areas)
- Drops parcels in zip codes we treat as structurally illiquid for a first-few-deals buyer — remote, thin local markets, or areas dominated by bonded special assessments that survive a tax sale.
- 4. Bulk-owner clusters
- Drops parcels tied to speculator-style portfolios — the same owner name on eight-plus parcels in a sale — plus a curated blocklist of known speculator entities sitting just under that threshold. We flag the shape, not the person; we don't publish owner names.
- 5. AVM-ratio filter
- Drops a parcel when its opening bid already exceeds half its estimated market value. It needs a valuation to fire — so on a list we haven't fully enriched, it correctly does nothing. A filter with no data to evaluate is a no-op by design, not a clean pass.
- 6. (Reserved structural checks)
- Additional structural flags (TRA suffix, owner type, condo-style addressing) are computed and surfaced as risk badges rather than hard drops, because they're judgment cues — not reasons to delete a parcel automatically.
What the signals mean — and their limits
- Situs address
- Strong, simple, decisive. Its limit: it occasionally removes a legitimate adjacent-owner opportunity — a deliberate trade for hours of saved time.
- Minimum bid
- A coarse proxy for "is this in my range." It says nothing about whether the price is fair — that's what the (mostly unrun) valuation layer is for.
- TRA suffix
- A flag, not a detector. A non-baseline TRA can mean a Mello-Roos overlay — or a different school district, a 1915-Act assessment, a fire/water district, or an annexation boundary, with no special tax at all. Confirm on the secured tax bill; the dollar amount is never derivable from the TRA code.
- Owner type / bulk pattern
- Catches speculator dumps and commercial owners. Its limit: a few legitimate residential portfolios fit the bulk pattern too — those we flag for a deliberate look, not an automatic skip.
- Automated valuation (AVM)
- A third-party model's estimate, not ours. Frequently wrong on atypical properties. Treat every enriched number as a starting hypothesis to verify, not a fact — and right now, most of our survivors don't carry one at all.
- Trap badges (HOA-FWD, CONDO, ENV-RISK, etc.)
- Pattern recognition from address and owner fields. They tell you what to check, not what's true. An ENV-RISK badge means "run a Phase I," not "this is contaminated."
What's still on you — every parcel, every time
The filters shrink the search space. They do not replace the work below, which applies to any tax-sale candidate.
- Pull the parcel on the county GIS; confirm zoning, lot size, and frontage.
- Order a title chain and look for liens that survive the sale — federal tax liens especially.
- (What survives the deed and what's wiped out — including HOA dues, the recorded community rules (CC&Rs), and Mello-Roos special taxes — is covered, with primary sources, in the research posts.)
- Get a current title report from a service that issues policies on tax deeds.
- Physically inspect, or at minimum review recent satellite and street-view imagery.
- Determine occupancy. The deed is yours; the eviction is still your problem.
- Check environmental records (EnviroStor, GeoTracker) for any parcel with a hint of past commercial use.
- Confirm the minimum bid hasn't changed at the auction platform on the morning of the sale.