An interest-only jumbo mortgage lets you pay only the interest on a large home loan for a set number of years. The payment is lower in that period because principal is scheduled for later. When the period ends, the full balance is repaid over the years that remain, and the payment steps up: from $16,266.67 to $27,176.61 a month in the example below. The loan works well when that later payment has a planned source from the first day.
A jumbo loan is defined by its size, an interest-only loan by its payment
Each year the Federal Housing Finance Agency sets the largest loan that Fannie Mae and Freddie Mac will buy from lenders. For 2026 that limit is $832,750 for a one-unit property in most of the country, and up to $1,249,125 in high-cost areas, with higher figures in Alaska, Hawaii, Guam and the U.S. Virgin Islands. The Consumer Financial Protection Bureau (CFPB) calls any larger loan a jumbo. Because it cannot be sold to those two buyers, each lender sets its own terms and pricing.
The CFPB defines an interest-only mortgage as a loan with scheduled payments that require you to pay only the interest for a specified amount of time. The amount you owe does not go down with each payment. When the period ends there are three ways forward: repay the balance at once, refinance, or begin monthly payments of principal and interest.
An interest-only loan also sits outside the Qualified Mortgage category. The CFPB lists an interest-only period among the features a Qualified Mortgage cannot have. Lenders can still make the loan. They have to assess your ability to repay it, and each one decides how much of this lending it wants to do.
The payment has two phases, and the arithmetic is short
Take the reference loan used across this site: $3,200,000 on a 30-year term, with the first 15 years interest only, at a fixed 6.1%. The rate is an assumption for illustration. It is not a rate offer.
In the first phase you pay one month’s interest on the full balance.
$3,200,000 × 0.061 ÷ 12 = $16,266.67 a month
In the second phase the balance is still $3,200,000, and it is repaid in the 180 months that are left. The standard amortization formula uses the monthly rate, r, which is 0.061 ÷ 12.
payment = balance × r ÷ (1 − (1 + r)^−180)
= $16,266.67 ÷ 0.5985540
= $27,176.61 a month
| Measure | Interest only for 15 years | Fully amortizing 30-year loan |
|---|---|---|
| Monthly, years 1–15 | $16,266.67 | $19,391.83 |
| Balance at the end of year 15 | $3,200,000.00 | $2,283,355.89 |
| Monthly, years 16–30 | $27,176.61 | $19,391.83 |
| Principal repaid by the end of year 30 | $3,200,000.00 | $3,200,000.00 |
The early payment is $3,125.16 a month lower than the payment on an ordinary 30-year loan of the same size, which is 16.12%. The step-up in year 16 is $10,909.94 a month, or 67.07%. Interest is charged on the full balance for the first fifteen years, so the loan carries more interest in total than one that amortizes from the first month. What that buys is the lower early payment and the capital it leaves free.
The right-hand column is the standard loan. It was built for buyers who need to borrow as much of the price as they can and repay it from salary, a little each month. An interest-only structure suits a different borrower: one with capital, who can decide in advance what repays the principal and when.
The length of the interest-only period sets the later payment
The interest-only payment is the same however long the period lasts. What changes is how many years are left to repay the principal.
| Interest-only period | Payment after it ends | Step-up |
|---|---|---|
| None | $19,391.83 | none |
| 5 years | $20,813.70 | 27.95% |
| 7 years | $21,594.84 | 32.76% |
| 10 years | $23,110.79 | 42.07% |
| 15 years | $27,176.61 | 67.07% |
Every row is $3,200,000 at a fixed 6.1% on a 30-year term.
The rate matters as much as the period. Some interest-only loans carry an adjustable rate, and then the later payment depends on where the rate stands when amortization begins. On the same loan after fifteen years, a rate of 7.1% makes the payment $28,941.70 a month. At 5.1% it is $25,472.40.
The reference loan assumes a fixed rate for all thirty years and a fifteen-year interest-only period. Both are assumptions. A lender’s term sheet confirms the pattern and the rate for your case.
The plan for year 16 is made at purchase
The CFPB’s three options are worth a second look, because they are not the same kind of thing.
Repaying the balance at once means having $3,200,000 liquid in year 15. Refinancing means qualifying again, at the rates and the home value of that year. Both depend on conditions that are set later. The third option, the scheduled payment, is the one written into the loan. A sound plan is built on it and names what pays it.
Some borrowers plan to pay down principal voluntarily during the interest-only years. If that is your plan, ask how the lender applies extra payments and whether the required payment is recalculated afterward.
What the interest-only years do on the balance sheet
The balance stays level. After fifteen years you owe $3,200,000. Principal repayment is scheduled for years 16 to 30.
Cash flow is freed. The payment is $3,125.16 a month lower than on an ordinary loan for the first fifteen years, and the capital that would have gone to principal stays available to you.
The plan rests on the scheduled payment. The CFPB’s guidance is not to count on selling or refinancing when the payment increases. A plan built on the scheduled payment, with its source identified at purchase, follows that guidance.
The tax deduction has a limit. IRS Publication 936 allows a deduction for home mortgage interest on the first $750,000 of debt taken out after December 15, 2017, or $375,000 if married filing separately. On a $3,200,000 loan the deduction covers part of the interest. Confirm your own position with your CPA.
Lenders qualify you on the later payment
This part is easy to miss. For a consumer mortgage with an interest-only period, Regulation Z tells the lender how to measure your ability to repay. It must use the fully indexed rate or the introductory rate, whichever is greater, and substantially equal monthly payments of principal and interest that repay the loan over the term left when the interest-only period ends.
The regulation’s commentary gives an example. A $200,000 loan at a fixed 7% allows interest-only payments for five years. The scheduled payment is $1,167 a month for those five years and $1,414 afterward. The lender must assess the borrower against $1,414.
Apply that to the reference loan. The lender has to be satisfied that you can carry $27,176.61 a month, not $16,266.67. The interest-only period improves your cash flow for fifteen years, and the household is qualified on the later payment from the first day. Lenders for loans of this size also weigh liquid assets, and the lender for your case sets how it counts them.
Beyond the rule, each lender writes its own standards, because it is keeping the loan or selling it privately. Lenders commonly weigh the size of the down payment, your credit history, your documented income and the liquid assets you hold after closing. The specifics vary. Ask for them in writing, along with the rate type, the length of the interest-only period and any prepayment terms.
What a sound plan settles before closing
| Item | How it works | What is settled before closing |
|---|---|---|
| The payment step-up | The payment changes when amortization begins, by 67.07% in the example | Where the later payment comes from |
| The rate type | On an adjustable loan, the payment also moves with the rate | Fixed or adjustable, and for an adjustable loan the index, the margin and the limits on each adjustment |
| The home’s value | Equity in the early years rests on the down payment and the market | The size of the down payment and how long you plan to stay |
| Your earnings | The step-up may arrive after you have stepped back from work | A source for the later payment that does not depend on salary |
An interest-only jumbo makes sense in a few situations
It tends to fit when one of these is true.
- Your income is high and uneven, and you intend to repay principal in lumps when bonuses or distributions arrive. Check how the loan treats prepayments.
- A defined event is expected to reduce the loan, such as the sale of a business or another property, and you can carry the full payment in the meantime.
- You hold assets you prefer not to sell, and they are large enough to repay the loan.
- The source of the later payment is identified and funded at the start.
In each case the later payment has a named source before the loan closes. The fourth is the one a plan can be built around.
Where The Family Office Mortgage fits
The Family Office Mortgage uses this loan: a jumbo that is interest only for 15 years, then principal and interest for 15. The step from $16,266.67 to $27,176.61 is the same. The program does not change the mortgage. It adds a plan for the later payment.
That plan is a separately funded indexed universal life (IUL) insurance policy, with a bank financing part of the premiums. At purchase you contribute 30% of the price to the policy on top of the 20% down payment. In the $4M reference case that is $2,000,000 at closing. From year 16, projected policy cash of $370,000 a year is designed to fund the $326,119.29 annual payment. Committing more at closing is the advantage a household with capital has, and this is the structure that uses it.
The plan is built with margin. Policy cash could come in 10% lower, at $333,000 a year, and still cover every mortgage payment. There are three debts, each on its own schedule: the mortgage, the bank’s premium-finance loan, which has a planned exit around year 15, and policy loans.
Every transaction is underwritten by the team before it is proposed, and each case is modeled under a conservative risk profile and run through simulations across many market paths. After closing, policy values, the bank loan and the collateral are reviewed every year against the plan, so adjustments are made early. The team has done hundreds of transactions. The lender still qualifies you against the later payment in the usual way. The policy is the planned source of that payment, not a substitute for qualifying.
What is a Family Office Mortgage? explains the structure. The calculator runs it on your price, the comparison shows both paths year by year, and how the risks are managed covers the team’s part. Pairing an interest-only loan with a policy has a history, and the endowment mortgage lesson explains what this structure does differently.
