A home of $4M or more along Silicon Valley's mid-Peninsula corridor — Menlo Park, Palo Alto, Los Altos, Los Altos Hills, Woodside and Portola Valley, with Burlingame to the north and Los Gatos and Saratoga to the south — is financed in 2026 almost always with a jumbo mortgage, because the 2026 conforming loan limit in both Santa Clara and San Mateo counties is $1,249,125, the national high-cost ceiling. Many buyers here hold most of their wealth in employer stock and equity awards and would rather not sell it to buy; the financing question is how to commit capital without triggering a sale. One structure built for exactly that position is The Family Office Mortgage, a privately offered program that pairs a jumbo mortgage with a premium-financed indexed universal life insurance policy for households buying a home of $4M or more.
Why nearly every purchase here is a jumbo loan
Each year the Federal Housing Finance Agency sets the largest mortgage Fannie Mae and Freddie Mac may buy. For 2026 the limit is $832,750 for a one-unit home in most of the country and up to $1,249,125 in high-cost areas — 150 percent of the baseline, and the highest value the statute allows. The FHFA's published county list places both Santa Clara County and San Mateo County at that ceiling.
The arithmetic leaves no middle ground. A buyer who puts 20 percent down on a representative $5,000,000 home takes a $4,000,000 loan — more than three times the county limit. Across the price points that define this corridor, from roughly $4,000,000 for a well-kept ranch house on a good Palo Alto or Menlo Park street to eight figures for an acre in Los Altos Hills, Woodside or Portola Valley, every financed purchase is a jumbo, and many are several multiples of it.
Because a jumbo cannot be sold to the government-sponsored enterprises, each lender keeps the loan or places it privately and writes its own terms — down payment, reserves, rate structure. How an interest-only jumbo mortgage works covers that loan in detail.
How buyers here actually finance
The buyer pool is distinctive: households whose wealth arrived as restricted stock units, options and founder shares rather than as salary. Three patterns recur.
A large down payment, financed around the stock. Buyers commonly put 40% or 50% down — from vested shares already sold, from cash set aside, or from an earlier home's proceeds — and keep the remaining position intact. Selling several million dollars of low-basis stock creates a capital gains bill that never appears on the closing statement, so borrowing at a high down payment often beats liquidating. Lenders in this range underwrite the whole household: documented income, the assets that remain after closing, and the vesting schedule behind future grants.
Cash, then a mortgage. In competitive bidding, a cash offer removes the financing contingency, and some households close with cash and borrow afterward to restore liquidity. Delayed financing after a cash purchase describes that sequence.
Pledging instead of selling. Rather than sell positions, a buyer pledges investment assets to the lender or draws on a securities-based line. The portfolio stays invested and the tax event is deferred; what is added is a variable-rate debt against marketable securities, on which a market decline can bring a maintenance call. SBLOC, pledged asset line or mortgage compares the routes, and buy, borrow, die and where the home fits describes the strategy in full.
Within these, interest-only terms are common at this level: pay only the interest for a fixed period and decide deliberately what repays the principal.
The local costs that change the math
Property tax. Under Proposition 13, the base property tax rate in California is 1 percent of assessed value, plus the rates needed to pay voter-approved bonds and certain direct assessments, as the State Board of Equalization's overview lays out. A sale triggers reassessment to the price paid, so on a $5,000,000 purchase the 1 percent base alone is $50,000 a year, before bond rates. Those additions are real here: San Mateo County's Controller reports $399 million of bond debt service — much of it school-district bonds — on top of the county's $3.3 billion base levy for fiscal year 2024-25. Once established, the assessed value can generally rise no more than 2 percent a year, and the county issues a supplemental assessment covering the balance of the first tax year after a purchase.
Transfer tax. Both counties charge a documentary transfer tax of $1.10 per $1,000 of value — 55 cents per $500, per the county recorders — which is $5,500 on a $5,000,000 sale. Palo Alto is the exception in the corridor: under Chapter 2.34 of its municipal code it levies its own real property transfer tax of $3.30 per $1,000, and as a charter-city tax it draws no credit against the county tax, so a Palo Alto sale pays $4.40 per $1,000 — $22,000 on $5,000,000. Only three Santa Clara County cities have a city tax: San Jose, Palo Alto and Mountain View. On the San Mateo side, Menlo Park, Woodside, Portola Valley and Burlingame charge the county tax only; the neighboring estate towns differ, as the Atherton and Hillsborough page works through. By custom the seller pays the tax, and the allocation is negotiable in the contract.
The deduction limit. Federal law caps the home mortgage interest deduction at interest on the first $750,000 of debt, or $375,000 if married filing separately, for loans taken out after December 15, 2017, per IRS Publication 936. On a $4,000,000 loan the deduction reaches only a small share of the interest. Your CPA can state the after-tax cost of a given loan for your case.
Where the program fits
The program is candid about where it belongs in this market. It suits a household buying a home of $4M or more, holding $5M or more in assets beyond the home and earning $500,000 or more, that intends to keep the home and would rather commit capital up front than borrow the maximum — or sell a concentrated stock position to avoid borrowing. It is a poor fit for a buyer who needs full liquidity elsewhere or expects to sell within a few years.
On a $5,000,000 home at the program's standard terms, the household commits half the price at closing: $1,000,000 as the down payment and $1,500,000 as the contribution to the financial instrument. The mortgage — made by a third-party lender, because the program is not a lender, bank, insurance company or government program — is $4,000,000, interest only for the first fifteen years and principal and interest for the fifteen after. The rate is an assumption for illustration, not a rate offer: at an assumed 6.5 percent the interest-only payment is $21,667 a month, and in years 16 to 30 the scheduled payment is $34,844 a month. The financial instrument's projected payout is sized to that payment. The payout is a projection, not a guarantee; the mortgage still runs its full thirty years; designs are tested with no growth credited in their first two years, and the instrument's values are reviewed against the plan every year.
The trade is deliberate: $2,500,000 committed at closing, in exchange for fifteen years of the lower payment and a designed source for the later ones. Whether the structure beats paying cash, pledging a portfolio or taking a plain jumbo depends on the household, which is what the comparison and the calculator are for. The eligibility page states the criteria in full.
