How Mortgages Work
A complete primer on mortgage loans — from basic mechanics to the application process — so you can borrow with confidence.
What Is a Mortgage?
A mortgage is a loan specifically used to purchase real estate. Unlike an unsecured personal loan, a mortgage is secured by the property itself — meaning the home serves as collateral. If you fail to repay the loan, the lender has the legal right to foreclose on the property and sell it to recover the money owed.
When you take out a mortgage, the lender pays the seller, and you get the keys. You then repay the lender in monthly installments over a set term — commonly 15 or 30 years. Each payment covers the interest that accrued on your outstanding balance, plus a portion that reduces the balance itself. This gradual payoff process is called amortization.
The Main Types of Mortgages
Not all mortgages are alike. Understanding the major categories helps you choose the right loan for your situation.
Fixed-Rate Mortgages
The interest rate is locked in for the entire loan term. Your principal and interest payment never changes, which makes budgeting straightforward. The two most common terms are 15-year and 30-year. A 15-year loan pays off faster and costs less in total interest, but the monthly payment is higher. A 30-year loan stretches payments out, lowering the monthly amount but costing significantly more over time.
Adjustable-Rate Mortgages (ARMs)
ARMs start with a fixed introductory rate — often lower than fixed-rate loans — for an initial period such as 5, 7, or 10 years. After that, the rate adjusts periodically (typically annually) based on a market index like SOFR. If rates rise, your payment goes up; if they fall, your payment drops. ARMs carry rate caps that limit how much the rate can change per adjustment and over the life of the loan.
Government-Backed Loans
- FHA loans — Insured by the Federal Housing Administration; require as little as 3.5% down and accept lower credit scores. They require mortgage insurance for the life of the loan in most cases.
- VA loans — Guaranteed by the Department of Veterans Affairs; available to eligible veterans, active-duty service members, and surviving spouses. No down payment required and no PMI.
- USDA loans — For homes in eligible rural and suburban areas; no down payment required and below-market interest rates for qualifying borrowers.
Jumbo Loans
Jumbo loans exceed the conforming loan limits set by Fannie Mae and Freddie Mac (currently $806,500 in most of the US for 2026). Because lenders cannot sell these loans to the GSEs, they carry stricter qualification requirements and typically slightly higher interest rates.
How Mortgage Interest Works
Interest is the cost of borrowing money, expressed as an annual percentage rate (APR). On a mortgage, interest accrues monthly on your outstanding balance.
Your fixed monthly payment is calculated so that the loan is fully paid off by the last month of your term. In the early years, most of the payment goes toward interest because the balance is large. Over time, as you pay down principal, the interest portion shrinks and the principal portion grows — even though the total payment stays the same. This is the essence of amortization.
Example: $300,000 loan, 7.00%, 30-year fixed
| Monthly payment (P+I) | $1,995.91 |
| Month 1 interest | $1,750.00 |
| Month 1 principal | $245.91 |
| Month 180 interest | $1,158.42 |
| Month 180 principal | $837.49 |
| Total interest paid (30 years) | $418,527 |
Understanding Amortization
Amortization is the process of paying off a loan through regular payments that cover both interest and principal. On a fully amortizing loan (the standard US mortgage), each payment is calculated so the balance reaches exactly zero on the last payment.
The amortization schedule is a complete table of every payment — showing how much goes to interest, how much reduces the balance, and what the remaining balance is after each payment. Reading this table is eye-opening: on a 30-year loan, you do not reach the 50% payoff point until roughly year 21 because early payments are so heavily weighted toward interest.
Use our Amortization Calculator to see your full payment schedule and how extra payments can shorten your term.
The Mortgage Application Process
Getting a mortgage involves several steps, each of which takes time. Understanding the sequence helps you plan ahead and avoid delays.
Step 1 — Check Your Finances
Lenders evaluate four key factors: credit score, debt-to-income ratio (DTI), down payment, and employment history. A credit score of 620 is typically the minimum for conventional loans; 740+ gets you the best rates. Your DTI — monthly debt payments divided by gross monthly income — should generally be below 43%, and ideally below 36%.
Step 2 — Get Pre-Qualified or Pre-Approved
Pre-qualification is a quick, informal estimate of what you might borrow. Pre-approval is a formal review of your finances that results in a written commitment from the lender. Pre-approval is much stronger and is expected by most sellers in competitive markets.
Step 3 — Shop for Lenders
Rate differences between lenders can be significant. Get quotes from at least three lenders — banks, credit unions, and mortgage brokers. Compare both the interest rate and the APR (which includes fees). Multiple credit inquiries for a mortgage within a 45-day window count as a single inquiry for credit-scoring purposes.
Step 4 — Submit Your Application
Once you have a property under contract, you formally apply. You will provide tax returns, pay stubs, bank statements, and documentation of any other income or assets. The lender will order an appraisal to verify the home's value supports the loan amount.
Step 5 — Underwriting and Closing
An underwriter reviews your full file and either approves, suspends (needs more info), or denies the loan. If approved, you receive a Closing Disclosure at least three business days before closing. At closing, you sign a mountain of documents, pay closing costs, and receive the keys.
Pre-Approval vs. Pre-Qualification
These terms are often confused but they are meaningfully different:
- Pre-qualification: Takes 5–10 minutes online. Based on self-reported data — no credit check, no document verification. Gives you a rough idea of what you might afford but carries little weight with sellers.
- Pre-approval: Requires documentation and a hard credit inquiry. The lender actually verifies your income, assets, and debts. Results in a formal letter stating a maximum loan amount and rate. Valid for 60–90 days. Sellers and agents expect this before taking your offer seriously.
Key Mortgage Terms to Know
- Principal — The amount of money you borrow (not counting interest).
- Interest rate — The annual cost of the loan, expressed as a percentage.
- APR — Annual Percentage Rate; includes fees, making it a better comparison tool than rate alone.
- Escrow — An account held by the lender to collect and pay property taxes and insurance on your behalf.
- PMI — Private Mortgage Insurance; required when you put less than 20% down on a conventional loan.
- Loan-to-Value (LTV) — Your loan amount divided by the home's value; lower LTV means better rates and no PMI.
- Points — Prepaid interest that reduces your rate; 1 point equals 1% of the loan amount.
- Closing costs — Fees and prepaid expenses due at closing, typically 2–5% of the loan amount.