The whole thing in one paragraph
A mortgage is a loan secured on a property. You borrow an amount, you pay it back over an agreed period with interest, and if you do not, the lender can take the property to recover the money. Everything else — the products, the acronyms, the fee schedules — is variation on those two sentences.
Why the early payments barely touch the debt
Interest is charged on what you still owe. At the start you owe almost the whole sum, so most of a payment is interest and only a sliver reduces the principal. As the principal falls, the interest charged falls, so more of each identical payment goes to the debt. That is amortization, and it is the source of two facts that surprise people: after several years of payments the balance has barely moved, and overpayments made early are worth far more than the same amount paid later, because they remove interest for every remaining year.
Term is a trade, not a detail
A longer term means a smaller monthly payment and a larger total cost, because the money is borrowed for longer. A shorter term means the opposite. Neither is correct in general. The honest question is which risk you would rather carry: the strain of a larger payment, or the cost of paying interest for another decade. Many loans allow overpayment, which effectively lets you take a long term for safety and repay on a short one when you can.
Fixed and adjustable
A fixed rate holds for a defined period, sometimes the whole term and sometimes only the first few years. It buys certainty, and you pay for that certainty in the rate. An adjustable rate moves with a reference rate, usually within limits on how far and how fast. It starts cheaper and hands you the risk.
The important question with any fixed period shorter than the term is what happens at the end of it. That is a scheduled event, and it is worth knowing the date and the fallback arrangement from the beginning rather than discovering both a month before.
What is actually in the payment
- Interest on the outstanding balance.
- Repayment of principal, unless the loan is interest-only.
- Property taxes, where the lender collects and holds them in escrow.
- Building insurance, and any mortgage insurance required when the deposit is small.
Comparing quotes on the interest rate alone is therefore comparing part of the object. The annual cost measure that includes fees is a better comparison, and the schedule of fees is better still.
What underwriting is testing
Underwriting looks like a judgement of you and is really an estimate of two probabilities: that you will keep paying, and that the property will still cover the debt if you do not. That is why lenders care about the stability of income as much as its size, about existing commitments, about how much of the price you are contributing, and about anything unusual in the building itself. A property a lender considers hard to resell is treated as a risk even when the borrower is not.
The words you will meet
| Amortization | The schedule by which a loan is repaid, and the reason early payments are mostly interest. |
|---|---|
| Escrow | Money held by a third party for taxes, insurance or a pending transaction. |
| Loan-to-value | The loan as a proportion of the property's value. Lower usually means better terms. |
| Origination fee | A charge for setting the loan up, sometimes rolled into the balance. |
| Points | A payment made up front to reduce the interest rate. |
| Prepayment penalty | A charge for repaying early. Worth checking before planning overpayments. |
None of this is guidance about which loan to take. It is the vocabulary, so that the conversation with a lender is about your circumstances rather than about definitions.