ORIGINAL HOLDING-PERIOD ANALYSIS
If you sell in year 10, the remaining balance matters
Comparing 120 payments with 600 payments answers a lifetime-cost question. A household planning to move after ten years needs a common horizon. At that point the shorter loan is repaid, while the longer loan still carries ₩283,529,512 of debt. A smaller monthly payment has postponed principal repayment.
Hold HF's published rates fixed. Change only the loan amount; the slider does not test borrowing eligibility.
| Measure | 10-year loan | 50-year loan |
|---|---|---|
| Monthly payment | ₩3,167,322 | ₩1,404,938 |
| Cash paid in 120 months | ₩380,078,624 | ₩168,592,504 |
| Principal repaid | ₩300,000,000 | ₩16,470,488 |
| Interest paid | ₩80,078,624 | ₩152,122,015 |
| Balance still owed | ₩0 | ₩283,529,512 |
The longer term frees ₩1,762,384 a month, but leaves ₩283,529,512 to repay after year 10.
Monthly rate = annual percent ÷ 1,200. Payment = P × r ÷ (1 − (1 + r)−n). Balance at month k is the present value of the remaining n − k payments. Values are calculated before rounding.
What the apparent saving leaves out
For the original ₩300M scenario, the fifty-year loan uses ₩211,486,120 less cash during the first decade, but incurs ₩72,043,392 more interest during that same decade. If the property is sold then, the outstanding balance must be settled from sale proceeds or other funds. A comparison based only on monthly outflow misses this obligation.
This is a nominal financing comparison. We do not assume that the monthly difference is invested, assign it a guaranteed return, or forecast a sale price. Discounting, fees and early repayment charges could change an individual's preference. The two official HF endpoint rates are used as published; neither term is promised to a particular borrower.
For a housing budget, combine the payment with separately evidenced management costs and taxes. The APT field replay shows why missing management data must remain visible.
Download the dated inputs and observed outputs (JSON). The file distinguishes official values, tool observations and controlled assumptions. It contains no personal borrower or employee data.
INPUT AND EVIDENCE LEDGER
Put the two cases on the same footing.
| Field | Value | Origin |
|---|---|---|
| Principal | ₩300,000,000 | Controlled comparison input |
| 10-year endpoint | 4.90% fixed / 120 payments | HF September 2026 published rate |
| 50-year endpoint | 5.20% fixed / 600 payments | HF September 2026 published rate |
| Repayment | Equal monthly principal and interest | APT calculation rule |
DECISION READING
Read the gap, not just the winner.
The 50-year endpoint cuts the scheduled payment by about 56%, but the modeled lifetime interest is about ₩462.9M higher. The lower monthly figure cannot be presented without the term and total-payment layer.
REPRODUCIBLE WORK
The comparison ledger.
| Check | Formula or rule | Result |
|---|---|---|
| 10-year payment | P × r(1+r)^n ÷ ((1+r)^n−1) | ₩3,167,322 per month |
| 50-year payment | Same formula; 600 periods at 5.20% | ₩1,404,938 per month |
| Monthly relief | ₩3,167,322 − ₩1,404,938 | ₩1,762,384 |
| Scheduled interest | Total scheduled payments − ₩300M | ₩80.1M over 10 years versus ₩543.0M over 50 years |
SOURCE SNAPSHOT
Official context and the limited role it supports.
SENSITIVITY
Conditions that can reverse the gap.
- Eligibility, age, property value, and product rules can make one term unavailable.
- Early repayment would change the lifetime-interest comparison.
- The two rates are official endpoint rates, not a quote for this borrower.
HUMAN ACCOUNTABILITY + AI USE RECORD
The owner is accountable; the technical checks were AI-assisted.
The TOOOLBOX site owner authorized the publication scope and remains the correction contact. AI assistance was used for drafting, implementation, arithmetic recomputation, and source-link checks. This record does not claim line-by-line human fact-checking or licensed professional review.
- Record ID
- TB-APT-10-20260907
- Owner role
- TOOOLBOX site owner and developer
- Technical check date
- 2026-09-07
- Human fact-check
- No separate human fact-check recorded
- AI use
- Drafting, code, arithmetic, and link checks
- Correction channel
- Public contact page
- Opened the HF release and matched both endpoint rates and terms.
- Recomputed all 120- and 600-period payment totals independently.
- Added eligibility and early-repayment boundaries before publication.
BOUNDARIES
Claims this comparison cannot support.
- This calculation excludes fees, insurance, prepayment charges, and underwriting.
- It does not recommend a term or establish eligibility.
- Rates can change after the cited September 2026 publication.
MORE APT DECISION NOTES
Test the result yourself.
This note preserves a dated calculation. Change the inputs in the live workspace, or compare another evidence pattern below. Live source availability and results can differ from the dated example.