The Quick Read: On a fixed-rate loan, the payment usually steps up by roughly a fifth to a third when amortization begins, and the percentage is the same at $4M as at $400K. Only the dollar amount scales with the balance, so the real question is whether the property’s rent still covers the larger payment on reset day.
- The jump is set by the note rate, the length of the interest-only window, and the years left to repay principal.
- A shorter repayment tail means a bigger jump. A longer tail softens it.
- The balance does not fall during the interest-only window, so the full $4M is re-amortized at reset.
- Coverage that looks comfortable on interest-only can fall near or below 1.00x afterward.
- Rent growth, reserves, and the exit plan matter more than the loan size.
How Big Is the Jump?
Expect an increase from the low 20s to the high 30s in percent on common fixed-rate structures. A consumer-style calculator comparison from Calcinum shows the pattern on one loan. A 5-year interest-only period into 25-year amortization raises the payment about 21%. A 7-year window into 23 years raises it about 28%. A 10-year window into 20 years raises it about 33%.
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Rate source: Freddie Mac 30-yr average via FRED® — Federal Reserve Bank of St. Louis · effective Oct 15, 2026
Prefilled with starting assumptions — enter your own rent or nightly figures, taxes, insurance, and HOA for a more accurate picture.
Program parameters update from Lendmire’s centralized guideline source. Taxes and insurance are editable estimates.
As of Oct 15, 2026 · General Freddie Mac market benchmark, not a Lendmire loan offer. Rent, nightly rate, occupancy, taxes, and insurance are editable estimates. Short-term rental figures are estimates only and vary significantly by season, property type, management approach, and local short-term-rental rules — confirm local regulations before relying on them. Qualifying income for short-term rentals varies by program — some use appraisal market rent, others use documented STR history or projections — and is confirmed in underwriting. Not a Loan Estimate, approval, or commitment to lend. Program availability and eligibility are subject to lender guidelines, credit approval, property review, and underwriting.
Those figures are illustrative examples at an assumed rate, not program quotes. They still show the rule that matters. The shorter the amortization tail, the harder the step-up.
Loan size does not change the percentage. Payment is proportional to balance, so a $4M loan and a $400K loan with the same rate and tail jump by the same percent. The dollar increase is about ten times larger on the bigger loan, and it lands on one date.
The note rate also shapes the percentage. A higher note rate makes the jump somewhat smaller, because interest already makes up more of the interest-only payment. Whatever the rate, the structure is what drives the result.
Key Terms Defined
Interest-only period: The stretch of months when the payment covers interest alone and the balance stays flat.
Amortization: The schedule that repays principal and interest together over a set number of years.
Recast (reset): The date the payment is rebuilt to repay the full balance over the years remaining.
ITIA: Interest, taxes, insurance, and association dues, the payment base used to test coverage on an interest-only loan.
Coverage ratio: Monthly rent divided by the monthly housing obligation. A ratio of 1.00x means rent equals the obligation.
Tail: The years of amortization left after the interest-only window ends.
How the Payment Is Rebuilt, Step by Step
The reset follows a fixed sequence, and each step can be checked against the note.
1. The interest-only payment equals the balance times the annual rate, divided by twelve. Taxes, insurance, and any association dues sit on top of that.
2. The balance stays flat. No principal is repaid, so on reset day the balance is still $4M.
3. The full balance is re-amortized over the months left in the note. A 30-year note with a 10-year window leaves 240 months to repay the whole amount.
4. The rate stays the same on a fixed-rate note. The step-up comes only from squeezing the same balance into fewer years.
5. Taxes, insurance, and dues do not step up because of the reset. Only the principal-and-interest piece changes.
That last point matters for coverage. The whole housing obligation rises by less than the principal-and-interest jump, because part of it never changes.
What the Underwriter Tests
Across the wholesale network Lendmire places files with, the interest-only test is run on ITIA. Select programs qualify an interest-only $4M file on that payment, subject to lender guidelines and underwriting. The window is typically 120 months on 30- and 40-year terms, with leverage capped at 75% on a standard investment-property loan, and coverage of at least 0.75x on the test payment.
Some programs in the market instead test coverage at the fully amortizing payment. Confirm which payment the program uses before you model anything. The two tests can produce very different ratios from the same rent.
Qualification runs primarily on property-level rental income covering the payment, subject to lender guidelines. That is why the post-reset math belongs in the file before commitment, not after.
Consider a modeled example. Assume a property clears 1.30x on the interest-only test. Assume interest makes up about 80% of ITIA and the rest is taxes, insurance, and dues. A 33% jump in principal and interest raises the whole obligation by about 26%, and coverage falls to roughly 1.03x. These are modeled assumptions, not market data.
Now start from 1.10x instead. The same step-up would pull coverage to about 0.87x, below the 1.00x benchmark most standard programs are built around. Select lenders in the network do review sub-1.00 coverage in some cases, but leverage and terms adjust, subject to underwriting.
To hold coverage flat through the reset in the first example, rent would need to rise by about the same 26%. That is the hurdle rent growth has to clear during the interest-only window.
What a $4M Balance Adds to the File
Size changes the program envelope, not the reset math. Through select wholesale programs, a $4M balance sits in the $3M-$4M band. On an investment-property purchase or rate-and-term refinance, leverage typically tops out at 65%. Cash-out is not available above $3M. All figures are ceilings, subject to underwriting and not a commitment to lend.
Above $4M, every request is reviewed case by case before submission. Purchase and rate-and-term leverage is 60% on review, with no cash-out.
Other conditions that usually come with this size:
- A credit score of 700 or higher above $3M, with a clean housing history.
- Two appraisals on any loan above $2M.
- Six months of reserves on the subject property, counted on ITIA for interest-only loans. First-time investors typically hold twelve.
- Citizens or permanent residents only at this size, no rural property, and entity vesting welcome without layered entities.
Reserves deserve a second look at $4M. Six months of ITIA is the program floor. A reserve plan that accounts for the larger post-reset payment is a separate, prudent step.
Structures and Variations
The same $4M balance can reset very differently depending on the note.
| Structure | Typical step-up |
|---|---|
| 5-year IO, 25-year tail | About 21% (illustrative) |
| 7-year IO, 23-year tail | About 28% (illustrative) |
| 10-year IO, 20-year tail | About 33% (illustrative) |
| 10-year IO on a 40-year note | Smaller; 30-year tail |
The 40-year structure is the lever worth understanding. With a 120-month window on a 40-year term, the tail is 30 years instead of 20, so the step-up is meaningfully smaller. The tradeoff is more total interest over the life of the loan.
An adjustable rate adds a second source of change. The OCC’s consumer publication on interest-only mortgages notes that most interest-only plans in the consumer market carry adjustable rates. Its payment-shock warnings, “double or triple,” are aimed at that setup. A fixed-rate investor loan with a 20- to 30-year tail sits in a different range, as the table shows.
DSCR vs. conventional financing
There are two common ways to finance an investment property, and they qualify you differently — here’s how investors weigh them.
Why investors choose it
- Qualifies on the property’s rental income — no personal tax returns, W-2s, or pay stubs needed to document income.
- No personal debt-to-income ceiling to clear, so existing mortgages and obligations don’t cap your borrowing the same way.
- Can be closed in an LLC, keeping the property inside a business entity.
- Built for scaling — not held to the limit on number of financed properties that conventional financing applies.
- Underwriting centers on the deal: generally qualifies when the rent covers the payment, a 1.00x coverage ratio being a common baseline (confirmed in underwriting).
- Designed specifically for investment property, including long-term and, where the program allows, short-term rentals.
Where it’s strong
- Often the lowest ongoing financing cost for a buyer who fully qualifies on personal income — a fit for a first property or a cost-first purchase.
Trade-offs for investors
- Requires full personal income documentation and must fit within a debt-to-income limit — salary, existing debts, and other mortgages all count.
- Typically held in your personal name rather than a business entity.
- Caps how many financed properties you can carry, which can become a ceiling as a portfolio grows.
- Evaluates you as a borrower as much as the property, which usually means more paperwork.
How investors usually choose: a first or single property often optimizes for the lowest financing cost; portfolio builders often optimize for leverage, vesting in an LLC, and scaling past conventional caps. The right answer depends on your goals, the property, and current guidelines — both paths run through select lenders in Lendmire’s wholesale network, with eligibility and terms confirmed in underwriting.
Where the General Rule Breaks
Restarted versus remaining-term amortization. Most notes amortize over the years that remain. The OCC example works this way: a 30-year loan with a 5-year window repays principal over the next 25 years. A restart at a full 30 years would give a smaller payment, so read the note to see which applies.
Balloon structures. A loan can be interest-only to maturity with the full balance due at the end. There is no reset payment, but the whole $4M must be refinanced or paid off.
Negative amortization. This is a different animal. It happens when the payment does not cover interest and the unpaid amount is added to the balance. A standard interest-only investor loan covers all interest, so the balance stays flat.
Prepayment terms. A prepayment penalty can raise the cost of exiting early. Check the note before planning a sale or refinance ahead of the reset.
Coverage is not cash flow. A ratio above 1.00x compares rent to the housing obligation. It does not count repairs, vacancy, or management.
What the Decision Looks Like
Interest-only suits an investor with a defined plan. A short hold ending in a sale, a value-add property where rent is still ramping, or a refinance planned before the reset can all fit. A long hold with thin coverage may be better served by full amortization or the longer 40-year tail.
Plan the exit with care. The CFPB’s explainer on interest-only loans cautions borrowers not to assume they can sell or refinance if the payment increases, because property value and finances can change. A refinance-at-reset plan only works if the property and the borrower qualify then.
Equity also behaves differently. With no scheduled principal repayment in the window, equity growth comes from appreciation alone.
Before committing, run three checks:
- Model coverage at the post-reset payment, not just the interest-only payment.
- Size the rent growth needed to hold your target ratio.
- Confirm the exit works if values flatten.
For a closer look at how the lower payment lifts coverage in the first place, see Lendmire’s explanation of how an interest-only payment raises coverage compared with an amortizing one. The complete DSCR loans guide covers program basics. DSCR loans are designed for non-owner-occupied investment properties, so they are reviewed differently from a standard owner-occupied mortgage.
If you are buying or refinancing a high-balance rental property and want to see how the numbers work, Lendmire can help you compare super jumbo DSCR loan options based on the property income, the loan balance, credit profile, leverage, and investor goals. Lendmire is a broker arranging financing through select lenders across 41 markets, including Washington, D.C.
This article is general information, not legal or tax advice. Tax treatment can depend on how the funds are used and how the property is held; investors should keep clear records and speak with a qualified attorney or CPA before relying on any deduction.
Frequently Asked Questions
Does the rate change when a fixed-rate interest-only loan amortizes?
No. On a fixed-rate note the rate stays put, and the payment rises only because the same balance is repaid over fewer years. An adjustable-rate note can add a rate change on top of the reset.
Does the maturity date move when the interest-only period ends?
Usually not. The note’s term runs on its original schedule, and the interest-only window simply takes up the first part of it. The note and term sheet state the exact months, so confirm them before committing.
Does a $4M loan jump by a larger percentage than a smaller one?
No. Payment scales with balance, so the percentage depends on rate, window length, and remaining tail. A $4M loan has a much larger dollar increase, which is why reset-month cash flow deserves modeling in advance.
Can I count on refinancing before the reset?
Not safely. A refinance depends on the property’s value, your finances, and lender guidelines at that time. A plan that only works if a refinance is available is a risk to size before you close.
Does a 40-year note mean 40 years of interest-only?
No. On select programs, a 40-year note typically carries a 120-month interest-only window followed by a 30-year amortization. Some structures amortize over all 40 years instead, so check the term sheet.
Lendmire’s self-employed mortgages page presents both super jumbo programs, bank statement and DSCR, side by side.
About Lendmire
Lendmire, NMLS# 2371349, is a mortgage brokerage focused on investor financing, arranging DSCR loans in 40 states plus Washington, D.C. — 41 markets total. Qualification is based on the property’s income rather than personal income documentation, subject to lender guidelines, making it a fit for LLC-held rentals and scaling portfolios. Scotsman Guide named Lendmire a Top Mortgage Workplace in both 2025 and 2026.
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References
1. Calcinum – Interest-only calculator
2. OCC – Interest-Only Mortgage Payments and Payment-Option ARMs
3. CFPB – What is an interest-only loan?
This article is part of Lendmire’s super jumbo DSCR loan program — full qualification details, guidelines, and scenarios live on the program page.
Related reading: How to Document a Super Jumbo DSCR Loan · How a Luxury Investment Property DSCR Loan Works · How Much Can You Borrow With a Luxury Short-Term Rental DSCR Loan?
Brandon Miller
Founder & CEO, Mortgage Loan Originator, Lendmire LLC
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Disclosures. The information presented in this article is general market commentary, not financial, legal, or tax advice. Lendmire is a mortgage brokerage (NMLS# 2371349) — not a direct lender or depository institution — and loan placement is subject to lender underwriting. Nothing in this content represents a commitment to lend. Loan terms, pricing, and program availability vary based on borrower qualifications, property characteristics, and state of subject property, and are subject to change at any time. Lendmire complies with Equal Housing Opportunity requirements. Consumer access: nmlsconsumeraccess.org.