SPONSOR LLCs
Who built your building?
Who still owns part of it?
Every NYC condo and co-op was built by a sponsor — typically a single-purpose LLC formed in NY or Delaware. The sponsor controls the board until handover, retains units (sometimes for decades), and writes the offering plan that governs every future amendment. Sponsors don't disappear; they leave residual obligations and often, residual litigation exposure.
WHAT WE TRACK
For every sponsor LLC.
Each sponsor profile includes:
- Portfolio — every building this sponsor developed, with date of declaration, units, and 421-a vintage
- Control-period timeline — when sponsor handed each building over, units retained at handover, units retained today
- ACRIS deed chain — all transfers from sponsor to unit owners, plus inter-affiliate transfers
- Sponsor-affiliate litigation — NYSCEF cases naming any entity in the sponsor's known family
- Offering plan amendments — every AG REFB amendment chronologically
- NY LLC Transparency Act disclosures — as the 2026-01-01 effective-date data comes online
This is the data the new NY LLC Transparency Act requires sponsors to file as of January 2026. We're building the public-facing version because the state's filing portal is not searchable in a useful way.
PREVIEW
Five sponsors, sampled.
Full sponsor catalog in build; cross-referenced against ACRIS deed chains and AG REFB offering plan filings. Click through where a case study is published.
| Sponsor | Buildings | Units retained | Jurisdiction | Notable |
|---|---|---|---|---|
| Related Companies | 14 | 2 | NY | 15 Hudson Yards (BBL 1007027502); large 421-a vintage portfolio · case study → |
| Extell Development | 11 | 0 | NY | Multiple Billionaire's Row buildings; 421-a heavy |
| Toll Brothers City Living | 8 | 1 | Delaware (registered NY) | Mixed-tier condo conversions in Brooklyn and Manhattan |
| JDS Development Group | 6 | 3 | Delaware (registered NY) | 111 W 57th, 9 DeKalb; high-rise specialist |
| Stahl Real Estate | 5 | 4 | NY | Long-hold sponsor; retains significant unit positions post-handover |
Sample only. Comprehensive sponsor index in build queue.
WHY SPONSOR DATA MATTERS
The sponsor era doesn't end at handover.
Construction defects discovered three years after handover are sponsor liability. Offering-plan misrepresentations are sponsor liability. 421-a affordability cliffs that were inadequately disclosed at sale are sponsor liability. Statute of limitations for offering-plan misrepresentation in NY is six years from declaration — but the Martin Act tolling rules can extend exposure further.
For board members: knowing who the sponsor was, what they retained, and what they still owe is the foundation of any construction-defect action. For unit owners: knowing whether the sponsor still holds units changes the math on every common-charge vote. For journalists: sponsor portfolios are where the cross-building patterns live.
See the sponsor control-period abuses regulatory-gap page for the structural analysis. For the editorial deep-dive on the new disclosure regime, see the blog post "The NY LLC Transparency Act took effect — sponsor disclosure looks different now."