First edition · 2026
An Insider's Guide to Borrowing, Protecting, Investing and Building Wealth
The people who sell financial products were taught how they work. This book teaches you, from the side of the desk where they are priced.
New here?
A health check, a calculator, a checklist and the opening. Twenty minutes to see whether this is the book for you.
Open the free sampler →Already reading?
A focus timer, private notes, saved chapters, reflection questions and your progress. All kept on your device.
Open the Reading Room →A book, and what you can do with it
The book
Written by a banker, from the side of the desk where products are priced, sold and measured, and built so that you can check every claim and try every calculation yourself.
The lesson that was never on the timetable
Most adults are expected to make decisions about loans, cards, mortgages, insurance, pensions and investments that nobody ever taught them to make. The people selling those products were taught.
A 2014 survey of more than 140 countries found that only about one adult in three could answer at least three of four basic financial-concept questions (Klapper, Lusardi and van Oudheusden, 2015).
What you will actually learn
Inside the book
Turn the pages before you buy: from the opening, to a chapter’s ledger, to a worked calculation you can run yourself.
The Education Nobody Scheduled
Most adults are expected to make decisions about loans, insurance, pensions and investments that they were never taught to make. This book is the lesson that was never on the timetable.
Every working adult runs a small financial institution. Money arrives, some of it is committed before it lands, some is borrowed against, some is saved, and decisions are made, often in a few minutes at a bank counter or on a phone, that will shape the next twenty years.
Five questions
How long does this last, and what happens to the cost the longer it runs?
What does it really cost, all in, beyond the headline number?
What could go wrong, and who is left holding it if it does?
Who gains if I say yes, and how are they paid?
What else could I do with this money, including nothing?
Chapter 11 · The True Cost of Borrowing
The price of a loan is not the monthly payment. It is the total repaid minus the amount borrowed, plus fees, and it depends on whether the rate is flat or on a reducing balance.
Red Flag
A loan advertised only by its monthly payment.
Ask Before You Sign
Chapter Ledger
Remember
Ask
This week
Ask a lender to give the offer in writing, including the total repayable.
Illustrative case
David earns well and spends nearly all of it. There is a car loan, a card balance that never seems to shrink, and almost nothing set aside. Nothing is going badly wrong, and yet nothing is building. His situation is the clearest picture of the difference between income and wealth.
One month of David’s pay, as the companion models it:
Margin: 4%. A good income, and almost nothing left to build with.
Across the Desk
How it looks from inside the lender
Lenders look at more than pay: they look at how much of it is already spoken for. Two applicants on the same income can look very different once their commitments are counted.
That is why the book asks you to find your own margin before anyone else does.
Five people, five decisions
Do the Math
You borrow $10,000 for 24 months at 6% flat. Interest is charged on the full amount for the whole term:
Payment = (P + P × rate × years) ÷ n
= (10,000 + 10,000 × 6% × 2) ÷ 24 = $466.67
Interest paid: $1,200. But you are repaying the balance down as you go, so the same payment on a normal reducing-balance loan implies:
Equivalent rate11.1%
The picture
Flat interest keeps charging on the full $10,000 while what you actually owe shrinks.
Try It · about 20 minutes
Write each one once: what you owe, the yearly rate, and the minimum. Circle the most expensive.
| Debt | Balance | Rate | Minimum |
|---|---|---|---|
Then pay every minimum and send every spare amount to the circled one.
Second Look
A popular belief, tested
“A loan with a low monthly payment is a cheap loan.”
Verdict: Myth
Stretching the term lowers the payment and raises the total cost. Judge a loan by its total cost of credit.
Take it with you
An Insider's Guide to Borrowing, Protecting, Investing and Building Wealth
Prefer to explore first? Try the tools or browse the chapters.
Start with the opening, and the five questions that frame everything.
Read more of the opening →The Chapter Ledger gathers what to remember, what to ask, and what to do this week.
Open the Chapter 11 companion →Ideas land through five ordinary people, and a view from inside the institution.
Explore David’s case, with live numbers →Where a calculation matters, the book works it through and highlights the result.
Run this calculation with your numbers →Short exercises put your own figures on the page, and a popular belief gets tested.
Fill in the debt worksheet →Take it with you, or keep it by the desk where the decisions get made.
Page previews show the book’s recurring formats using this site’s own examples. They are not scans of the printed pages.
Why this book?
Most financial education is written from the customer’s side. This one is written by a banker, from where products are designed, priced, sold and measured, so you can see what the pitch leaves out.
Time, Cost, Risk, Incentives, Alternatives. A method that works on a loan, a policy, a fund or a pension, long after any single product has changed.
Examples are in US dollars as a neutral unit, and boxes compare how several countries handle the same question, so it travels with you across systems.
Claims are labelled as established fact, research finding, industry practice, general principle, interpretation or example, and each chapter has source notes.
It does not recommend products or promise returns. It teaches you to read the price, the risk and the incentive, then decide for yourself.
Cases to work through, calculations to run, exercises to fill in and checklists to take to the bank. The book, and this companion, are meant to be returned to.
The idea at the centre
Products change. Pitches change. The questions don’t.
How long does this last, and what happens to the cost the longer it runs?
What does it really cost, all in, beyond the headline number?
What could go wrong, and who is left holding it if it does?
Who gains if I say yes, and how are they paid?
What else could I do with this money, including nothing?
Try one now
One of the book’s central warnings, as a calculator. Change the numbers; switch “flat” to “reducing”; watch what the same headline rate really costs.
Character cases
Pick someone. See their situation, change their numbers, then run the same idea on your own life.
Tools & calculators
Every tool shows its formula, defines each variable, walks through a worked example, then lets you use your own numbers. Private by design: nothing leaves your browser.
Chapter 11 · The True Cost of Borrowing
Payment, total cost and effective rate, and what a flat rate really means.
BorrowOpen →Chapter 3 · The Price of Time
See what a lump sum and a monthly habit become, before and after inflation.
Save & growOpen →Chapter 13 · Mortgages and the Rent-or-Buy Question
Compare the money position after N years of renting versus buying.
BorrowOpen →Chapter 17 · Insurance: What to Protect, What to Absorb
Test whether a policy protects you from ruin or just sells you comfort.
ProtectOpen →Chapter 21 · The Cost of Investing
The same money in two products with different annual fees.
InvestOpen →Chapter 24 · Retirement Across Systems
Will your savings, plus other income, cover the life you want?
Plan aheadOpen →Most adults are expected to make decisions about loans, insurance, pensions and investments that they were never taught to make. This book is the lesson that was never on the timetable.
Every working adult runs a small financial institution. Money arrives, some of it is committed before it lands, some is borrowed against, some is saved, and decisions are made, often in a few minutes at a bank counter or on a phone, that will shape the next twenty years.
New on the companion
Update
A focus timer, private notes, saved chapters, reflection questions, insight cards and an everyday calculator, all kept on your device.
Resource
The Five Questions pocket card, the four worksheets and the book-club guide as PDFs.
Update
Pick a real-life moment (borrowing, cards, a home, irregular income…) and get the chapters, tool and case that help.
The Reader’s Letter
Practical money insights, new tools, calculators and resources to help readers make better financial decisions. Sent only when there is something genuinely useful to share: a few times a year, never more.
Subscribe and get The Financial Decision Toolkit free: a decision worksheet, questions to ask for six kinds of product, a red-flag checklist, a money snapshot and a formula sheet. See what is inside
Thank you. Your toolkit is ready.
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Before your next money decision
Read it once for the argument. Come back to it, and to the tools, whenever a bank, an insurer or an adviser puts something in front of you.
Money, Explained From the InsideA. Allazim
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