30-Year vs Interest-Only DSCR Loan Structures
A standard 30-year DSCR loan amortizes principal and interest from day one. An interest-only structure defers principal for a set period — commonly 10 years — lowering the monthly payment and raising the DSCR during that window, then converts to a fully amortizing payment (over the remaining term) once the IO period ends.
NightYield Editorial
STR-DSCR research & underwriting desk
Published 2026-07-27
How the payment differs during the interest-only period
On a fully amortizing 30-year loan, every payment includes both interest and a principal component from month one — the balance shrinks a small amount every month. On an interest-only structure, the payment during the IO period covers interest only; the loan balance doesn't decrease at all during that window.
Because the payment is lower with no principal component, PITIA is lower too — which directly raises the DSCR compared to the same rate and balance fully amortized. This is one of the more common levers used to push a marginal deal above a lender's floor without changing the property's rent.
What happens when the interest-only period ends
Once the IO period expires — commonly after 10 years on a 30-year-term IO structure — the payment recalculates to fully amortize the original balance over the remaining term, not the original term. Because none of the balance was paid down during the IO years, that remaining-term amortization schedule produces a materially higher payment than a loan that had been amortizing all along.
| Payment during years 1-10 | Payment after year 10 | Balance at year 10 | |
|---|---|---|---|
| 30-year fully amortizing | Level payment throughout | Same as before | Meaningfully reduced |
| 10-year IO / 30-year term | Lower, interest-only | Steps up — amortizes over remaining 20 years | Unchanged from origination |
That step-up is the trade-off: the DSCR looks better throughout the IO period, but the loan is carrying the full original balance right up until the day it converts, at which point the payment jumps to amortize that full balance over a shorter remaining window than a standard 30-year schedule would have.
When interest-only makes sense
It tends to fit strategies built around cash flow now and a planned exit or refinance before the IO period ends — maximizing DSCR cushion and monthly cash flow during a hold, with the balloon-like payment step-up addressed by selling or refinancing rather than riding it out. It's a weaker fit for a buy-and-hold-forever strategy where the step-up will eventually need to be absorbed by rent growth alone.
- Model both structures' DSCR and monthly cash flow at the same rate and balance side by side.
- If choosing interest-only, build a concrete plan for what happens at IO conversion — refinance, sale, or confirmed rent growth covering the step-up.
- Confirm the exact conversion mechanics (remaining term, recalculation method) in the specific loan's documents.
- Don't treat the IO-period DSCR as the loan's permanent ratio — model the post-conversion payment too.
Key takeaways
- Interest-only payments have no principal component, lowering PITIA and raising the DSCR during the IO period.
- The balance doesn't decrease during interest-only years — it's unchanged right up to conversion.
- After the IO period ends, the payment steps up to amortize the full original balance over the remaining term.
- Interest-only fits a plan with a defined exit or refinance before conversion, more than a hold-forever strategy.