Mortgage Planning
Mortgage Affordability Stress Tester Common Mistakes
Ten easy-to-make mistakes, plus quick fixes and sanity checks, so your scenarios stay consistent and comparisons stay clear.
Published: January 1, 2026 · Updated: January 1, 2026 · By FinToolSuite Editorial
Open the stress tester
Run a clean scenario after fixing inputs and compare to your previous run.
Disclaimer
- Educational only. No guarantees. Numbers are illustrative.
10 common mistakes
- Mixing monthly and annual income. Fix: Use consistent units. Sanity check: Income aligns with pay frequency.
- Skipping debts. Fix: Add monthly debts. Sanity check: DTI includes all obligations.
- Forgetting property tax or HOA. Fix: Add costs. Sanity check: Costs reflect your market.
- Ignoring PMI/LMI thresholds. Fix: Enter percent and threshold. Sanity check: LTV matches your down payment.
- Underestimating maintenance. Fix: Add a monthly allowance. Sanity check: Compare low/high cases.
- Not rerunning after edits. Fix: Rerun every change. Sanity check: Outputs reflect current inputs.
- Reading default probability as a forecast. Fix: Treat it as directional. Sanity check: Compare scenarios, not absolutes.
- Comparing scenarios with different assumptions. Fix: Change one input at a time. Sanity check: Labels note what changed.
- Over-precision on decimals. Fix: Round conservatively. Sanity check: Inputs are simple and clear.
- Using stale assumptions. Fix: Update rates, taxes, and fees. Sanity check: Note dates in labels.
FAQs
Do mistakes change exports?
Yes. Rerun and re-export after fixing inputs.
Should I keep old scenarios?
Keep labeled versions but note outdated assumptions to avoid confusion.
Where is privacy info?
See Privacy Policy.
Fix and rerun
Open the mortgage affordability stress tester, clean your inputs, rerun, and save a new scenario.