How Mortgages Work: A Complete Guide to Home Financing

A mortgage is a loan secured by the house it buys. If the payments stop, the lender can take the property back through foreclosure. That collateral is the reason mortgage rates run so far below credit card and personal loan rates. Most of this guide follows one example so the numbers stay concrete. Alex buys a $400,000 house with $40,000 down and borrows the remaining $360,000 at 6.75% for 30 years. The principal and interest payment is $2,335 a month. Property taxes add about $367 a month where Alex lives (a 1.1% tax rate), homeowners insurance adds roughly $150, and because the down payment was under 20%, private mortgage insurance adds another $180 or so. The real monthly cost is close to $3,032. Keep that gap in mind whenever a calculator shows you a payment: the loan itself is only part of the bill. The loan repays through amortization. Each month, the payment first covers the interest that accrued on the balance, and whatever remains reduces the principal. In month one, interest on $360,000 at 6.75% is $2,025, so only $310 of Alex's $2,335 payment touches the balance. The split improves slowly and then quickly. Over the full 30 years, Alex pays about $480,000 in interest on top of the $360,000 borrowed. That total is why a quarter point of rate is worth arguing over, and why this guide spends a whole section on shopping.

A fixed-rate mortgage keeps one rate for the whole term. Alex's 6.75% stays 6.75% from the first payment to the last, which makes budgeting simple and is the main reason the 30-year fixed is by far the most common American mortgage. An adjustable-rate mortgage (ARM) starts with a lower fixed rate for an introductory period, then moves with a market index. A 5/6 ARM, for example, holds its rate for five years and then adjusts every six months, subject to caps on how far it can climb per adjustment and over the life of the loan. An ARM can work if you are confident you will sell or refinance before the fixed period ends. If you are wrong about that, you carry the rate risk. FHA loans, insured by the Federal Housing Administration, accept down payments as low as 3.5% with credit scores of 580 and up. The trade-off is mortgage insurance that, with less than 10% down, lasts for the life of the loan. Program details are on HUD's FHA page. VA loans serve military service members, veterans, and eligible surviving spouses. No down payment, no monthly mortgage insurance, and rates that are often the lowest available. A one-time funding fee of roughly 1.25% to 3.3% applies, and it can be rolled into the loan. USDA loans cover moderate-income buyers in eligible rural and suburban areas, also with nothing down. Jumbo loans sit at the other end: anything above the conforming limit set each year by the Federal Housing Finance Agency, currently a bit over $800,000 in most counties. Jumbos usually want stronger credit and bigger down payments.

The process starts before house hunting does. Pre-approval means a lender reviews your income, debts, and credit, then states in writing how much it will lend. The letter usually lasts 60 to 90 days, and sellers expect to see one attached to an offer. The paperwork is predictable: pay stubs from the last 30 days, W-2s or tax returns for two years, two or three months of bank statements, and a list of your debts. Self-employed borrowers should plan on two years of tax returns plus profit-and-loss statements, and more questions. Once a seller accepts your offer, the formal application begins. Within three business days the lender must send a Loan Estimate, a standardized form that lays out the rate, payment, and every fee. The CFPB's Buying a House guide walks through the form line by line and is worth reading before you get your first one. The lender then orders an appraisal, verifies your employment, and sends the file through underwriting, where a person or an automated system makes the final call. Application to closing typically takes 30 to 45 days. During that window, hold still financially. No new credit cards, no financed furniture, no car loan, no job change if you can avoid it, and no large unexplained deposits. Lenders re-check credit shortly before closing, and any of these can stall or kill the approval.

Underwriting mostly comes down to a credit score, a debt-to-income ratio, and a loan-to-value ratio. The credit score summarizes your borrowing history on a scale that tops out at 850. Conventional loans generally want 620 or better, and pricing improves meaningfully above 740. Payment history and current balances drive most of the score. Debt-to-income (DTI) compares monthly debt payments to gross monthly income. Lenders compute it two ways. The front-end version counts only housing costs. Alex earns $11,000 a month before taxes, so the $3,032 housing bill is a 27.6% front-end ratio, just under the traditional 28% guideline. The back-end version adds all other debts. With a $600 car payment, Alex's back-end DTI is 33%, comfortably below the 43% to 45% ceiling most programs apply. Loan-to-value (LTV) is the loan amount divided by the appraised value. Alex borrowed $360,000 against a $400,000 house: 90% LTV. Anything above 80% on a conventional loan triggers private mortgage insurance, which protects the lender, not you. Alex's PMI runs about $180 a month. PMI does end. Once the balance falls to 80% of the original value, you can request cancellation, and the servicer must drop it automatically at 78%. On Alex's schedule, with no extra payments, the 80% mark arrives around year eight. Extra principal payments or a rise in the home's value can move that up. FHA loans work differently: with less than 10% down, the insurance premium stays until you refinance out of the loan.

Closing costs generally run 2% to 5% of the loan amount, so Alex should expect somewhere between $7,200 and $18,000 on top of the down payment. The range is wide because the mix varies by state and lender. The big line items: an origination fee (often 0.5% to 1% of the loan), the appraisal (around $400 to $700), title search and title insurance (a few hundred to a few thousand dollars), recording fees, and attorney fees in states that require one. Then come the prepaids: several months of property taxes and insurance deposited into escrow, plus interest from the closing date to the end of that month. Escrow deserves a short explanation because it confuses new buyers. The servicer collects a slice of taxes and insurance with every payment, holds it, and pays those bills when they come due. Once a year the account gets analyzed. If your tax bill rose, the monthly payment rises too, sometimes with a catch-up amount for the shortage. A "fixed" mortgage payment is only fixed on the principal and interest portion. Two ways to soften the cash hit at closing. Sellers can agree to pay part of your costs, called concessions, usually capped between 3% and 6% of the price depending on the program. Or the lender can charge a slightly higher rate in exchange for a credit toward costs. Three business days before closing you receive a Closing Disclosure with final numbers. Compare it against the Loan Estimate and question anything that grew.

Freddie Mac research has found meaningful savings from comparing multiple quotes, and the mechanics of Alex's loan show why. The quarter point between 7% and 6.75% is worth $60 a month on a $360,000 balance, about $21,600 over the full term. One afternoon of applications is well paid at that rate. For context on where rates stand in a given week, Freddie Mac publishes a national average survey every Thursday. Compare APR, not just the note rate. APR folds most fees into a single figure, so a 6.5% loan with heavy origination charges can carry a higher APR than a 6.75% loan with light ones. The Loan Estimate makes side-by-side comparison straightforward: look at origination charges and lender credits specifically, since third-party fees like the appraisal will be similar everywhere. Discount points are prepaid interest. One point costs 1% of the loan and typically buys about a quarter point of rate. Alex could pay $3,600 to drop from 6.75% to 6.5%, cutting the payment from $2,335 to $2,275. Saving $60 a month against a $3,600 cost means breaking even at the five-year mark. Points only make sense if you will keep the loan longer than that. Get quotes from at least three different kinds of lenders: a bank, a credit union, and an online lender or broker. Cluster the applications within two weeks and credit scoring treats the inquiries as one. Your own bank may or may not be competitive. Loyalty is not priced in.

Taking the first quote is the expensive one, and the previous section priced it: $21,600 on Alex's loan for a quarter point left on the table. Borrowing the full approval amount is a quieter mistake. A lender approving Alex for $450,000 says nothing about childcare, retirement savings, or the fact that Alex wants to travel. The approval is a ceiling, not a recommendation. Keeping the all-in housing payment near 25% of take-home pay leaves room for a life. Skipping the inspection to sweeten an offer trades a $300 to $500 report for the chance of a five-figure surprise in the foundation, roof, or plumbing. Even in a competitive market, an inspection for information only (without a contingency) beats going in blind. Emptying savings for the down payment leaves nothing for the water heater that fails in month two. A reasonable floor is three months of the full housing payment in reserve after closing, and moving costs and furniture on top of that. Finally, budget for the house, not the loan. Between taxes, insurance, PMI, utilities, and maintenance of roughly 1% to 2% of the home's value per year, Alex's $2,335 loan payment is really a $3,500 monthly commitment once everything is counted. Run the whole number before signing.

Refinancing swaps your current mortgage for a new one, and it makes sense when the new terms beat the old ones by enough to cover the cost of the swap. Closing costs on a refinance usually land between 2% and 3% of the loan. Say rates fall to 5.75% six years into Alex's loan, when the balance is about $332,600. A new 30-year loan at that rate carries a $1,941 payment, $394 less per month. But it also restarts the clock: six years of progress traded for a longer runway and more total interest. A 20-year refinance at 5.75% is the more interesting option here. The payment works out to almost exactly the original $2,335, and the loan finishes four years sooner than the old schedule. Same monthly cost, shorter debt. The break-even test settles most refinance decisions. Divide the closing costs by the monthly savings. If the refinance costs $8,000 and saves $394 a month, the break-even is about 20 months; stay in the house past that and the deal pays for itself. If you might sell before break-even, skip it. Cash-out refinancing borrows more than you owe and hands you the difference, typically for renovations or consolidating expensive debt. It has its uses, but the collateral is your house, and a bigger balance at closing costs plus a possibly higher rate deserves more skepticism than the marketing suggests. One more timing note. Late in a loan's life, most of each payment is principal. Refinancing at that stage into a fresh 30-year term can raise total interest even at a lower rate. Match the new term to the years you had left, or fewer.