A mortgage is the biggest loan most people will ever take on, yet almost no one explains how it works before you sign. Strip away the jargon and it is simple: a mortgage is a loan secured by your home. If you stop paying, the lender can take the house. Everything else — rate, term, escrow, points, insurance — is just detail that decides what you pay each month and over the life of the loan.
Principal and interest: what you owe and what it costs
Principal is the amount you borrowed. Interest is what the lender charges you to borrow it, expressed as an annual rate. Your monthly payment covers both, but not evenly. Through a process called amortization, early payments go mostly toward interest and only a little toward principal. As the balance shrinks, that flips — later payments knock down principal much faster. That is why paying a little extra in the first few years, when it goes almost entirely to interest, has an outsized effect on the total you pay.
Your rate and your term work together
Two numbers shape the cost more than anything else: the interest rate and the loan term.
- The term is how long you have to repay — most commonly 30 years, sometimes 15. A 30-year loan has a lower monthly payment but costs far more in total interest. A 15-year loan costs more each month but saves a large amount over time.
- Fixed vs. adjustable. A fixed-rate loan keeps the same rate for the whole term. An adjustable-rate mortgage (ARM) starts lower, then can rise or fall after an initial period — cheaper up front, less predictable later.
Rates move constantly with the broader market. Freddie Mac publishes a weekly national average you can track at its Primary Mortgage Market Survey, but your own rate depends on your credit, down payment, and loan type — treat any headline number as a rough guide, not a quote.
Rate vs. APR, and points
The interest rate is the cost of borrowing the principal. The APR (annual percentage rate) folds in certain fees — lender charges, points, and more — so it is usually a bit higher than the rate and is a better tool for comparing two offers apples to apples. Points are optional up-front fees, each roughly 1% of the loan, that buy your rate down. They can pay off if you keep the loan long enough to recover the cost, and waste money if you sell or refinance first.
The full monthly payment: PITI and escrow
Your real payment is bigger than principal and interest. Lenders usually bundle in property taxes and homeowners insurance and collect them monthly into an escrow account, then pay those bills for you when they come due. The industry shorthand is PITI — principal, interest, taxes, and insurance. If your down payment is under 20%, you will likely also pay PMI (private mortgage insurance), which protects the lender, not you, and can usually be removed once you build enough equity. This all-in number, not the principal-and-interest quote, is the one your budget should be built around.
DTI and getting pre-approved
Before a lender approves you, they check your debt-to-income ratio (DTI) — your monthly debt payments divided by your gross monthly income. Lower is better, and most programs look for a DTI comfortably under the low-to-mid 40s percent. A pre-approval is the lender's written estimate of what you can borrow, and it makes your offer far stronger because sellers know your financing is real. This is educational information, not financial advice — a licensed lender can price your exact situation.
Once you know your numbers, the next step is a great local agent who can connect you with trustworthy lenders. Getting matched on Homegrity is always free for buyers — we never resell your information and placement is never for sale. See our buyer guide or get matched with a local agent. You can also read whether renting or buying is cheaper and how down-payment assistance can lower your cash up front. For a deeper reference on loan types, the CFPB's Owning a Home guide is a solid, unbiased resource.
Frequently asked questions
What is the difference between interest rate and APR?
The interest rate is the cost of borrowing the loan principal. The APR includes the rate plus certain lender fees and points, so it is usually slightly higher and is the better number for comparing two offers side by side.
Do I really need 20% down?
No. Many loans allow 3–5% down. Putting down 20% lets you avoid PMI, but it is not required to buy. See our guide to down-payment assistance for programs that can lower your up-front cash.
What is escrow?
An escrow account is where your lender collects a share of your property taxes and homeowners insurance each month, then pays those bills for you when they are due. It is why your monthly payment is larger than principal and interest alone.
How much home can I afford?
Lenders look at your debt-to-income ratio, credit, and down payment. A pre-approval from a licensed lender is the most accurate way to learn your real budget — this article is educational and not financial advice.
