CartelCheck

Paste your rent renewal notice and CartelCheck checks it against the pricing software your landlord's property manager was just caught coordinating through — and tells you if your city lets you fight it.

Problem

On November 26, 2025, RealPage settled with the Department of Justice over software that let competing landlords set rents off the same private data feed — no fine, no admission of guilt, but a court-appointed monitor and a list of features the company agreed to strip out. Since then a private tenant lawsuit, Gomez v. Greystar, has tested a San Francisco ordinance directly against a specific management company's software use, and more than a dozen cities have passed their own bans with a right for tenants to sue on their own. None of that reaches a renter holding a lease-renewal notice with a rent bump 20% above what CPI would explain. They have no way to check if their building's manager is named in any of these cases, whether their city even has a law that applies, or what to do before the renewal deadline passes.

Target user

A renter in a multi-unit building run by a regional or national property manager, roughly 25 to 45, who just got a renewal offer well above what their own income growth or the neighborhood's listing prices would justify. They're not organizing a tenant union and they've never filed a legal complaint — they want one place that tells them if this is normal or worth fighting, and if it's worth fighting, what to send and to whom.

MVP scope

• Property-manager lookup against a sourced, citation-linked list of companies named in the DOJ complaint, state attorney general suits, and Gomez v. Greystar — flags only companies with a documented court filing behind them, nothing inferred.
• Jurisdiction checker covering the growing list of cities and counties with algorithmic-pricing bans and a private right of action (San Francisco, San Diego, Berkeley, Santa Ana, Philadelphia, Minneapolis, Providence, Jersey City, Hoboken, Seattle, King County, Spokane, Portland) plus New York's statewide software ban.
• Renewal-notice log: photograph or paste each notice; the app timestamps the rent, the percent increase, and any occupancy language the notice discloses.
• Opt-in, anonymized neighbor matching — when enough renters in the same building or zip code submit a renewal in the same 30-day window, the app surfaces how many, how much, and how close together.
• Demand-letter generator for jurisdictions that allow a private right of action, pre-filled with the specific ordinance, the user's own renewal history, and the property manager's documented software use where it applies.
• A plain-language page explaining exactly what the DOJ settlement requires RealPage to change, so a user can tell "still doing the old thing" from "actually stopped."

Monetization

Freemium. Free tier covers the property-manager lookup, jurisdiction checker, and renewal-notice log. Paid tier ($6.99/mo, or $15 per generated document) unlocks the neighbor-matching flag, the demand-letter generator, and a referral to a tenant-rights attorney in jurisdictions where that's worth offering — attorneys pay a referral fee per qualified lead, the same model DoNotPay and similar legal-adjacent apps already run on.

Why now

Gomez v. Greystar, filed in the Northern District of California in July 2026, is the first known private lawsuit that puts a specific landlord's alleged RealPage/Yardi use directly against a city's ban — a test case renters can point to instead of a hypothetical. The DOJ settlement from November 2025 is the first time RealPage's actual pricing coordination got described in a legal filing rather than a news investigation, giving CartelCheck's flags something concrete to cite. And the list of cities with a tenant right to sue over this has more than doubled since early 2025 — Berkeley, Santa Ana, Minneapolis, and Portland all added bans in 2026 alone — which means the legal tool renters need now actually exists in a growing number of places; they just don't know it.

Risks & open questions

• Renters in an active lease with their landlord may be too worried about retaliation to use a tool that puts them on record, even in cities where retaliation itself is illegal.
• Naming a property manager as a RealPage/Yardi user has to stay strictly tied to actual court filings — anything looser risks a defamation claim against the operator, not just the landlord.
• The jurisdiction and property-manager lists both need monthly upkeep as new cities pass ordinances and new suits name new defendants; this is closer to a maintained legal database than a ship-once app.
• The neighbor-matching feature is the most useful part and the hardest to bootstrap — it needs several renters in the same building before it says anything, and most buildings won't hit that in year one.
• Will renters actually pay for a demand letter over just moving out? Moving is the default response to a bad renewal, and this only wins if fighting the increase is genuinely less effort than packing.

Next step

Build the jurisdiction and property-manager lists for five cities from public court filings, then test them against 20 real renewal-notice posts pulled from r/AskLandlords and r/personalfinance to see how often a named manager actually shows up. If the match rate is meaningfully above chance, promote to a weekly prototype.

Sources

• https://www.morganlewis.com/pubs/2026/08/algorithmic-rent-pricing-litigation-expands-under-new-state-and-local-laws — city-by-city list of 2026 algorithmic-pricing bans and the Gomez v. Greystar filing.
• https://www.propublica.org/article/doj-realpage-settlement-rental-price-fixing-case — DOJ-RealPage settlement terms announced November 26, 2025.
• https://www.credaily.com/briefs/realpage-sues-new-york-over-ban-on-rent-pricing-tools/ — New York's statewide software ban (GBL §340-b) and RealPage's First Amendment challenge.