SB 1211 for Fourplex / 4-unit in Rancho Cucamonga
Rancho Cucamonga's SB 1211 math for fourplex / 4-unit owners: 4 detached ADUs (the §66323 cap), plus 1 interior conversions. Total: 5 new homes. At Rancho Cucamonga's median rent of $2,100/mo, that's ~$126K in additional gross annual rent.
The Rancho Cucamonga scenario
Run it as a sequence: stabilize existing 4 units → permit 4 detached ADUs ministerially under §66314 → convert 1 interior space into rentable units → re-tenant at Rancho Cucamonga medians.
Rancho Cucamonga-specific note: Inland Empire upper market.
Small multifamily (2–4 unit) design playbook
Small multifamily lots are usually constrained on width before they're constrained on count. With a 4-unit existing footprint, the binding constraint becomes side-yard setbacks (4 ft min) and the 18-ft height limit. Two-story stacked-flat ADUs over surface parking are the highest-yield typology.
Pro-forma snapshot
| Existing units | 4 |
| Detached ADUs (SB 1211) | 4 |
| Interior conversions | 1 |
| Total new units | 5 |
| Median 1BR rent in Rancho Cucamonga | $2,100/mo |
| Est. additional gross rent | $126K/yr |
| Estimated total project cost | ~$1,344K |
| Year-1 NOI estimate | ~$95K |
| Stabilized cap rate at cost | 7.1% |
| Replacement parking required | No (§66313) |
| Approval pathway | Ministerial · §66314 |
| Typical permit timeline in Rancho Cucamonga | 60-100 days |
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