SB9 Rental Maxing in California

Member since 2026 · 2 posts · 0 votes

I have an opportunity to purchase a single-family house from my mother for a fantastic deal.

I'm interested in splitting the lot (ok under SB9) and building 2 units on each lot for a total of 4 units.

I'm planning on living in one of the units, and I'm estimating earning $2,000 - $4,000 in rent per unit that can cover the mortgage & other expenses and some positive cash flow per month.

Does anyone have any similar past experience with doing the SB9 split and maximizing the land for rental income?

If you had a similar opportunity, would you make the investment?

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Kasing Ng

Accountant · San Francisco, CA · Member since 2026 · 94 posts · 50 votes

1mo

Hi Dennis, hello from another Bay Area local. Local municipal review can add time to SB 9 lot splits, and it is worth factoring in the state mandate for a 3-year owner-occupancy affidavit. When you are modeling a four-unit stack, running a sensitivity check on the lower end of that rent range helps ensure the cash flow covers the debt service and operating costs.

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Kasing Ng
Accountant · San Francisco, CA · Member since 2026 · 94 posts · 50 votes
1mo
Hi Dennis, hello from another Bay Area local. Local municipal review can add time to SB 9 lot splits, and it is worth factoring in the state mandate for a 3-year owner-occupancy affidavit. When you are modeling a four-unit stack, running a sensitivity check on the lower end of that rent range helps ensure the cash flow covers the debt service and operating costs.
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- Dennis Morrow
  OP
  Member since 2026 · 2 posts · 0 votes
  1mo
  Thanks Kasing for your helpful insights.
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Alev Sharma
Woodland Hills, Los Angeles County · Member since 2026 · 17 posts · 2 votes
1w
Dennis, it can work, but the project is a lot bigger than the SB9 math suggests. A few things to pressure-test before committing:
- Owner-occupancy affidavit. For an SB9 lot split, you generally sign an affidavit that you intend to live in one of the units for 3 years. Confirm with San Jose planning how they apply it to your parcel.
- Unit count and size. SB9 allows up to two units per resulting lot, but check local objective standards, setbacks, and whether ADUs/JADUs can be added on top. Cities vary on this, and it changes your rent roll a lot.
- Construction cost vs. rent. Bay Area new construction often runs well into the hundreds of dollars per square foot once you add utilities, separate meters, impact fees and soft costs. Model it at the low end of your $2k-$4k rent range with today's construction loan rates and see if it still cash flows.
- Financing. Construction loans on lot-split projects are harder to get than a standard purchase loan. Talk to lenders before you close on the house.
- The family purchase. If you're buying below market from your mom, there can be gift and property tax reassessment implications. Worth a quick talk with a California CPA and a real estate attorney before you sign anything.
If the numbers still work after all that, it's a great way to turn one lot into long-term housing. Just budget for timelines that run longer than you expect.
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Ashish AcharyaBusiness Member
CPA, CFP®, PFS · FL · Member since 2017 · 5k+ posts · 3k+ votes
1w
Dennis, this is an interesting opportunity, especially in a market where adding housing units can significantly change the economics of a property.

Before committing, I’d look beyond just the projected rent and make sure the full development math works. The biggest questions are usually the cost to complete the split, construction costs, financing during the build, permitting timeline, carrying costs, and what the completed units will realistically be worth and rent for.

I’d also be careful about assuming every additional unit automatically creates positive cash flow. The value comes from whether the total project cost is justified by the additional income and long-term appreciation potential.

From the tax side, a project like this is worth planning before construction begins. How costs are tracked, how the property is held, depreciation basis, and when each unit is placed in service can all affect the future tax outcome. If you’re creating multiple rental units, getting the bookkeeping and documentation right from the beginning is important.

Feel free to DM me, I’d be happy to share a few resources on real-estate tax planning and development projects that may be helpful.
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Wilson Lau
Real Estate Agent · San Jose, CA · Member since 2023 · 182 posts · 104 votes
1w
Hey Dennis. SB9 is an amazing way to build wealth, and many of the builders and larger real estate funds are taking advantage of it to maximize their returns. By 2 units on each lot, I am assuming you are referring to another SFH + an ADU?
Keep in mind the process is not as straightforward, and there are many small details/ risk assessments you need to take into consideration (driveways, plumbing, electrical (PG&E can significantly delay your timeline), grading, retaining walls, etc...). What city are you in? Happy to discuss more in details.
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