A home of $4M or more on Seattle's Eastside — in Medina or Clyde Hill, on the western shore of Lake Washington — is financed in 2026 almost always with a jumbo mortgage, because the 2026 conforming loan limit for King County is $1,063,750, about a fifth of the representative $5,000,000 price. Buyers in these two small cities often bring concentrated technology-company holdings to the purchase, and a preference for keeping them intact. One structure built for that position is The Family Office Mortgage, a privately offered program that pairs a jumbo mortgage with a structured financial product 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. The FHFA's published county list places King County at $1,063,750 for a one-unit home — above the baseline because local home values run past it, below the ceiling.
The arithmetic leaves no middle ground. A buyer who borrows half the price of a $5,000,000 home takes a $2,500,000 loan, more than twice the county limit. Across the price points that define this market, from around $4,000,000 for a non-waterfront home on a shy quarter-acre to eight figures on the water in Medina, every financed purchase is a jumbo, and most are several multiples of the limit, the super-jumbo range.
The two cities are small and the character is consistent. Medina runs along the shoreline from Evergreen Point south, most of its value in lakefront lots. Clyde Hill sits on the ridge above, where the west-facing lots carry views across Lake Washington to Seattle and the Olympics. The neighboring towns of Hunts Point and Yarrow Point complete the cluster. Inventory is thin, waterfront is effectively fixed, and many sales are arranged quietly rather than broadly marketed. 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
Three patterns recur.
Cash or near-cash. A cash offer removes the lender from the negotiation, and in a thin market sellers value the certainty. The cost is liquidity: once several million dollars are in the house, they come back only through a sale or a new loan, and raising the cash by selling appreciated stock creates a capital gains tax bill that never appears on the closing statement. Paying cash versus financing works through that trade.
A jumbo sized to a large down payment. Buyers who could pay cash often borrow anyway, at 40% or 50% down, cutting the interest cost and keeping capital working. Lenders in this range underwrite the whole household: documented income, the assets that remain after closing, and sometimes pledged assets accepted in place of liquidated ones.
Borrowing against a portfolio. Rather than sell positions — often shares in a single technology employer — a buyer draws on a securities-based line or pledges investment assets to the lender. The portfolio stays intact 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. Buy, borrow, die and where the home fits describes that route and its risks.
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, rather than letting the loan decide it.
The local costs that change the math
Real estate excise tax. Washington taxes each sale of real property under a graduated real estate excise tax; the Department of Revenue's schedule applies to the state portion: 1.1% on the portion of the price up to $525,000, 1.28% up to $1,525,000, 2.75% up to $3,025,000 and 3% above that. A local rate is added on top, and the department's rate table effective May 1, 2026 lists 0.50% for both Medina and Clyde Hill. On a $5,000,000 sale the state share is $119,075 and the local share is $25,000, for $144,075 combined. The tax is customarily paid by the seller, though the department notes the buyer is responsible if it goes unpaid. The thresholds adjust every four years; the department has published the next set, for sales from January 1, 2027, which moves the top bracket's start to $3,051,000.
Property tax. King County assesses property at market value, updates values each year, and collects for the state, county, cities and taxing districts such as schools and fire districts. The rate for a parcel is the combined rate its levy area requires. State law caps the aggregate of regular levies at 1% of a property's true and fair value, per RCW 84.52.050, and voter-approved measures can sit on top. The practical point for a buyer here: the annual bill is set by the parcel's levy area and its voter-approved measures, so compare actual bills on candidate homes rather than assuming one rate across the two cities.
No state income tax, with a 2028 change. Washington does not currently have an individual income tax, per the Department of Revenue, which also notes a new 9.9% tax on adjusted gross income over $1,000,000 taking effect January 1, 2028, with the first returns due in 2029. A household at this market's income should have its CPA price both facts into the financing plan.
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 loan of several million dollars the deduction reaches only a small share of the interest.
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. It is designed around a person between 40 and 60 for the financial instrument. 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 about 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% 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 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, what a Family Office Mortgage is explains the structure, and how family offices finance a home describes it in family-office practice.
