An interest-only mortgage lets you pay just the interest for an initial period, keeping the early payment low. It sounds attractive, but during that period you build no equity from principal, and the payment rises sharply when the interest-only window ends. These loans suit specific situations and carry real risk for the unprepared.
How the structure works
For an initial period, commonly five to ten years, you pay only the interest on the loan, so none of the payment reduces the principal balance. Because you are not paying down principal, the early payment is noticeably lower than a comparable fully amortizing loan. When the interest-only period ends, the loan converts to fully amortizing, and you must repay the entire principal over the remaining, shorter term. Many interest-only loans also carry adjustable rates, adding another layer of payment uncertainty.
The payment shock later
The defining risk is the jump in payment when the interest-only period ends, sometimes called payment shock. Because principal now has to be repaid over fewer years than a standard 30-year schedule, the increase can be steep. If the loan is also an ARM and rates have risen, the new payment can be dramatically higher than the introductory one. Borrowers who do not plan for this can find the new payment unaffordable.
No principal equity during the interest-only period
During the interest-only years, you gain equity only if the home appreciates, not from paying down the loan. If home values stay flat or fall, you could owe nearly the original balance years into the loan. That leaves less cushion if you need to sell or refinance. This is a key difference from a standard loan, where every payment chips away at the balance from the start.
Who they can suit
Interest-only loans can fit borrowers with irregular or bonus-heavy income who want a low base payment and plan to pay principal in lump sums. They may also suit those confident they will sell or refinance before the interest-only period ends, or disciplined investors who will invest the payment difference. They are risky for buyers simply trying to afford a larger home than they otherwise could. The strategy only works with a clear, funded plan for the eventual principal repayment.
On a $400,000 interest-only loan at 6.5% with a ten-year interest-only period, the early payment is about $2,167, covering interest alone. When the period ends, the $400,000 must be repaid over the remaining 20 years, pushing the payment to roughly $2,983, a jump of more than $800. A borrower without a plan for that increase could be caught short.
Key takeaways
- Interest-only loans let you pay just interest for an initial period, keeping the early payment low.
- No principal is paid during that period, so you build equity only through appreciation.
- When the interest-only window ends, the payment jumps to repay principal over fewer years.
- Many are adjustable-rate, compounding the payment risk when the period ends.
- They suit disciplined or irregular-income borrowers with a plan, not those stretching to afford a home.
Common mistakes
- Using an interest-only loan just to afford a bigger home without a plan for the later payment jump.
- Forgetting that no equity accrues from principal during the interest-only period.
- Ignoring that an adjustable rate can push the post-period payment even higher.
FAQ
Can I pay principal during the interest-only period?
Usually yes, and doing so voluntarily builds equity and softens the later payment jump. Confirm your loan allows principal prepayment without penalty.
Are interest-only mortgages common?
They are far less common than after the 2000s housing boom and now face stricter qualifying standards. They are typically offered to well-qualified or higher-net-worth borrowers.