Guides & Data
Decision guides and original data studies, computed with the same engines as our calculators — so every claim comes with numbers you can verify yourself. Every break-even these studies produce is collected in The Break-Even Index, free to cite.
The Car Loan Deduction Dies at $111,000, Not $150,000 — and 0% Financing Kills It Outright
Original data: the 2025 car loan interest deduction phases out by a flat dollar amount, not a percentage. A typical car loan's deduction is worth nothing above a $111,000 MAGI. And 0% financing, having no interest, has nothing to deduct.
Read the guide →The Refund That Never Reaches You: What Cancelling a Car Warranty Actually Does
Original data: cancelling a financed extended warranty or GAP policy sends the refund to your lender, not to you — and your payment does not drop. We computed what it does instead, and what one unread clause in the contract is worth.
Read the guide →The Solar Loan Trap: A Fee You Were Not Allowed To Be Told, and a Payment That Jumps 47%
Original data: the 2.99% solar loan is bought with a dealer fee of 15–30% hidden in your price, and its payment assumes a tax credit you may not be able to use — or, after 2025, one that no longer exists.
Read the guide →Does Infinite Banking Work? Your Policy Earns 3.99%. The Illustration Just Never Says So.
Original data: we gave the policy the return its own sellers claim, and taxed the index fund on every dollar of gain. Buying term and investing the difference still finished $172,608 ahead.
Read the guide →The IUL Column Your Agent Did Not Show You Earns −9.98% a Year
Original data: every indexed universal life illustration prints two columns on the same page. One is a projection. The other is a promise. We computed the real annual return of both.
Read the guide →Balance Transfer Break-Even: When the Fee Pays for Itself — The Full Tables
Original data: exactly how many days of interest a 3% or 5% transfer fee buys back, the payment needed to clear the balance before 0% ends, and why a no-fee card can be the most expensive offer on the board.
Read the guide →0% Financing or the Cash Rebate? The Break-Even Map
Original data: the exact rate below which taking a car dealer’s cash rebate beats their 0% financing — mapped across every rebate size, term and price. Plus why the rule of thumb everyone repeats is calibrated to a car that barely exists any more.
Read the guide →15 vs 30 Year Mortgage: The Rate Discount Is Not the Point
Original data: only 15% of what a 15-year mortgage saves you comes from its lower rate. The other 85% comes from the shorter term — which a 30-year gives you for free, and lets you undo.
Read the guide →Mortgage Points vs a Bigger Down Payment: The 4-Point Ceiling Nobody Mentions
Original data: the advice to "put it toward the down payment and kill PMI" describes a choice most buyers do not have. Absorbing that cash in points would take 11.1 points — and lenders sell four.
Read the guide →Does Velocity Banking Work? We Modelled It Generously. It Is Worth $13 a Month.
Original data: velocity banking is not a scam — it beats plain extra payments by $1,835 over twelve years. But paying $25/month more beats it outright, every dollar of the benefit is the float, and below $102/month of surplus it turns on you.
Read the guide →The 28/36 Rule: What Debt-to-Income Ratio Do You Need for a Mortgage?
How the 28/36 rule works, the difference between front-end and back-end DTI, the ratios lenders actually accept today, and how to work out yours before you apply.
Read the guide →What Is a Balance Transfer Fee — and How Do You Calculate It?
What a balance transfer fee is, how to work out the exact dollar cost, the typical 3–5% range, when no-fee offers make sense, and the one number that tells you if it is worth paying.
Read the guide →How Much Interest Does a Credit Card Charge Per Day?
The daily interest math behind your credit card: what the daily periodic rate (DPR) is, worked examples at 24.99% APR, and how to get the daily charge to zero.
Read the guide →Pay Off Debt or Invest? A Decision Order That Actually Ends the Debate
The debt-vs-invest debate ends with an order, not a winner: employer match, emergency fund, high-APR debt, then a genuine choice. Here is the math.
Read the guide →How Do You Calculate Savings From Debt Consolidation?
How to calculate your real savings from debt consolidation by hand, and why a lower monthly payment is not the same as saving money.
Read the guide →HELOC vs Home Equity Loan: How to Decide in 5 Questions
Five questions that decide between a HELOC and a home equity loan — spending pattern, rate risk, payoff speed, discipline, and the fine print.
Read the guide →Minimum Payment Statistics: How Long Credit Card Debt Really Lasts
Original data: how many years minimum payments take at every common balance and APR, computed month by month — including the balances that never pay off at all.
Read the guide →Personal Loan or Balance Transfer? The Honest Answer for Card Debt
A one-number test decides most cases: can your budget clear the balance inside the 0% window? Here is how to answer it — and what to do when you can't.
Read the guide →What an Extra $100 a Month Does to Your Debt: The Full Tables
Original data: how much time and interest an extra $100/month cuts from a mortgage, student loans, an auto loan, a personal loan, and a credit card — including the debts it outright rescues.
Read the guide →How Is Your Credit Card Minimum Payment Calculated?
The two formulas US card issuers use to set your minimum payment, where your card's exact formula is written down, and why it matters at today's APRs.
Read the guide →Recast, Extra Payments, or Refinance? Where a Lump Sum Does the Most
A lump sum can lower your payment, shorten your loan, or fix your rate — three different moves. Here is how to pick the right one for your goal.
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