What is a mortgage (hipoteca)?

A mortgage is a loan specifically used to buy property, where the lender holds the property as collateral until the loan is fully paid. It allows individuals to purchase homes without paying the full price upfront.

How does a mortgage work?

A mortgage works by borrowing a set amount from a lender, which you repay monthly with interest over a fixed term. The property acts as security, and failure to pay can lead to foreclosure.

What are the common types of mortgages?

Common mortgage types include fixed-rate, where interest remains the same; variable-rate, with fluctuating interest; and mixed mortgages, combining both. Each type suits different financial situations and risk preferences.

What should I look for in a mortgage guide?

A good mortgage guide covers key topics like types of mortgages, application processes, interest rates, repayment plans, and legal considerations. It helps borrowers make informed decisions and avoid common pitfalls.

Why is understanding mortgages important?

Understanding mortgages is essential to choose the right loan, manage repayment effectively, and avoid financial risks like foreclosure. It empowers borrowers to navigate the property market confidently and secure favorable terms.

Complete Mortgage Guide: Types, Rates & Requirements

Variables

Loan amount

Principal borrowed (excluding down payment). Currency follows the active selector (USD, EUR, MXN, COP, ARS, CLP).

Annual rate

Fixed annual interest rate. Typical: 6.5% US conventional 30-yr, 3% Spain fixed, 10.5% Mexico bank.

Term

Years to pay off the loan. Common terms: 10, 15, 20, 25 or 30 years.

Monthly income

Optional. If you add it, we compute the payment-to-income (DTI) ratio banks look at when approving.

Practical example

Loan: $400,000 USD over 30 years at 6.5% fixed.

Monthly rate: 6.5 ÷ 12 ÷ 100 = 0.005417.

Number of payments: 30 × 12 = 360 months.

Monthly payment ≈ $2,528 USD.

Total paid: $2,528 × 360 = $910,000 USD.

Total interest: $910,000 − $400,000 = $510,000 USD — you pay 128% extra in interest over the principal.

Interpretation

If total interest exceeds the principal, consider shortening the term or negotiating the rate — long-term loans transfer enormous wealth to the lender.

Lenders typically reject loans where the payment exceeds 35% of monthly net income. Below 25% is comfortable.

Cutting the term from 30 to 15 years raises the payment ~30% but slashes total interest by ~60%.

Comparing two mortgages is more than comparing rates: check APR (or CAT/TAE in Latin America/Spain) which includes fees.

Assumptions and limitations

Fixed rate over the entire term. Adjustable-rate (ARM) or hybrid mortgages will have payments that change after the reset date.

Excludes origination fees, closing costs, taxes, and insurance (life, hazard) — budget those separately.

Excludes prepayments. Any extra payment to principal reduces total interest but is not modeled here.

The result is indicative. The final payment depends on the exact rate the lender approves after evaluating your profile.

When to use this calculator

Before visiting a lender, so you walk in with a realistic monthly payment range and don't accept the first rate offered.

To compare offers from multiple lenders holding loan amount and term constant — see which offer leaves less total interest.

When deciding between 15, 20 or 30 years. Seeing total interest per scenario typically changes the decision.

To validate the payment fits your income before falling in love with a property outside your real capacity.

To understand the effect of a larger down payment: lowering the loan amount cuts payment and interest non-linearly.

If you plan to make principal prepayments, simulate the shorter term (without extras) first to see if the base payment is workable.

Common mistakes

Looking only at the monthly payment, not total interest. A comfy 30-year payment can cost double the total of a tighter 15-year payment.

Forgetting closing costs: title, recording, transfer tax, origination fee, mandatory insurance. These can add 2-5% of the loan in the US, 8-12% in Mexico.

Not checking APR. Lenders compete on nominal rate but APR — which includes fees — can tell a different story.

Assuming future income will rise to justify a high payment today. Lenders assess your current situation; if income drops the payment doesn't.

Defaulting to the maximum term out of habit. In most cases, a 15-20 year term plus periodic prepayments comes out far better.

Industry use cases

First-time buyer (US)

$350,000 home with 20% down ($70,000). Loan of $280,000 over 30 years at 6.5% fixed: monthly payment ~$1,770. Need net income above $5,050/mo for the payment to stay at 35% DTI (lender soft cap).

Investor — rental property

$220,000 condo with 25% down. Loan of $165,000 over 15 years at 7%: payment ~$1,484/mo. If expected rent is $1,800-2,000, post-maintenance net cash flow is thin — raise down payment or shift markets.

Spain — first home

€250,000 flat with 20% deposit (€50,000). €200,000 mortgage over 25 years at 3.2% fixed: payment ~€969/mo. Real APR closer to 3.7% once tied insurance and pension plans are added.

Refinance after a rate drop

Current loan: $250,000 at 7.5% with 22 years left (payment ~$1,930). Refinance to 6.0% same term: payment falls to ~$1,710 — saves ~$58,000 in interest after closing costs.

Mexico — bank mortgage

$2.5M MXN home with 20% down. Loan of $2M MXN over 20 years at 10.5% fixed: payment ~$19,970/mo. Need ~$57,000/mo net income for the payment to stay within Infonavit/bank 35% cap.

Complete mortgage guide: types, rates, amortization, and the numbers that matter

A mortgage is the largest financial commitment most households take on. It is also one of the most opaque: banks present a TIN and a TAE, the notary reads a deed at speed, and the borrower leaves with a 20-30 year obligation they may not fully understand. This guide covers the mechanics, the formulas, and the 2026 rate environment for Spain and Mexico — the two markets where our simulator has the deepest local context.

The three mortgage types and when each makes sense

Fixed-rate mortgage (hipoteca fija)

The interest rate is locked for the entire term. Your monthly installment is the same in year 1 and year 23. In Spain (2026), fixed rates from the major banks sit at 3.2-4.0% nominal (TAE 3.5-4.3%). In Mexico, banks like BBVA, Santander, and Banorte offer fixed rates at 9.5-12.5% for peso loans.

Best for: borrowers who value payment certainty over the life of the loan, those with fixed incomes (public employees, salaried workers), or anyone who believes rates will rise from their current level.

Variable-rate mortgage (hipoteca variable)

In Spain, variable mortgages are indexed to 12-month EURIBOR (April 2026: 2.45%) plus a fixed spread (typically EURIBOR + 0.60-1.20%). Your installment resets annually when the EURIBOR reference is updated. When EURIBOR rises sharply (as it did from -0.5% in 2022 to a peak of 4.2% in late 2023), variable mortgage holders saw installments rise 30-50%.

Best for: borrowers who expect rates to fall over the loan horizon, those with short planned holding periods (plan to sell within 5-7 years), or those with financial flexibility to absorb payment variability.

Mixed mortgage (hipoteca mixta)

Fixed rate for an initial period (typically 3-10 years), then switches to EURIBOR + spread for the remainder. CaixaBank and ING offer popular 5- and 10-year fixed windows in Spain. It suits buyers who want short-term certainty but accept longer-term variability — typically when they expect income growth or plan early partial prepayment.

French amortization: the formula behind every monthly payment

Spanish and Mexican mortgages use French amortization (cuota constante): the monthly installment is constant, but its composition shifts over time. Early installments are mostly interest; later ones are mostly principal repayment.

Monthly installment formula:

C = P × [r(1+r)^n] / [(1+r)^n - 1]

Where: C = monthly installment, P = principal (loan amount), r = monthly interest rate (annual rate / 12), n = number of monthly payments (years × 12).

Worked example — Spain:

Loan: EUR 200,000
Term: 25 years (n = 300)
Rate: 3.5% fixed (r = 0.003517/month)
Monthly installment: EUR 1,001
Total paid over 25 years: EUR 300,300
Total interest: EUR 100,300 (50.2% of principal)

Worked example — Mexico:

Loan: MXN 2,000,000
Term: 20 years (n = 240)
Rate: 10.5% fixed (r = 0.00875/month)
Monthly installment: MXN 19,952
Total paid over 20 years: MXN 4,788,480
Total interest: MXN 2,788,480 (139% of principal)

The Mexican example underscores why mortgage calculators matter — many buyers see only the monthly payment and miss the total cost picture.

Down payment and transaction costs

Spain

Banks lend up to 80% of the appraised value (LTV 80%). Effective minimum down payment: 20% of purchase price + transaction costs of 10-12%:

ITP (property transfer tax on resale): 6-10% depending on Autonomous Community (Madrid 6%, Catalonia 10%, Andalucía 7%).
IVA (VAT) on new builds: 10%.
Notary + Land Registry + appraisal: 1-2%.

For a EUR 300,000 home: down payment EUR 60,000 + EUR 33,000-36,000 transaction costs = minimum liquid capital needed: EUR 93,000-96,000.

Mexico

Banks finance 70-90% of the property value (typically 80%). Standard transaction costs include:

Notary fees: 1.5-3% of property value (vary by state).
ISAI (Impuesto Sobre Adquisición de Inmuebles): 2-5% depending on state.
Appraisal: MXN 3,000-8,000.
Bank origination fee (comisión de apertura): 0.5-2% of loan amount.

INFONAVIT subscribers can apply their housing sub-account balance as enganche (down payment), reducing or eliminating the cash requirement for qualifying properties.

The document checklist

Spain (standard bank list):

DNI/NIE + passport, last 3 payslips or 2-year tax return (IRPF) for self-employed, CIRBE credit report (bank obtains it), most recent 6 months of bank statements, nota simple of the property, appraisal report (tasación, ordered by the bank).

Under Ley 5/2019, the bank must provide the FEIN (Ficha Europea de Información Normalizada) at least 10 business days before signing — this is the binding offer you compare across lenders. Before notary signing, both borrower and lender must attend a preliminary notary consultation (acta de transparencia).

Mexico (major bank list):

Official ID + CURP + RFC, payslips (last 3 months) or income verification letter (constancia de ingresos), bank statements (last 6 months), proof of address, employment letter, credit bureau authorization. For INFONAVIT co-financing: CESI (Carta de Elegibilidad de Subrogación de INFONAVIT) and employer registration with IMSS.

Refinancing: subrogación vs novación

Subrogación (Spain): transferring the mortgage to a new lender. The new bank pays off the original bank and sets new terms. Key cost: early-repayment penalty (comisión de amortización anticipada) capped by Ley 5/2019 at 0.25% in years 1-3 and 0.15% in years 4-5 for variable mortgages; 2% in years 1-10 for fixed, 1.5% after that.

Novación: modifying the existing mortgage with the same lender (rate, term, or amount). Usually lower cost than subrogación but subject to lender willingness.

Rule of thumb: refinancing makes sense when the rate reduction × remaining balance × remaining years exceeds the total switching costs.

Renting vs buying: the 200× price-to-rent rule

A practical heuristic: if the purchase price / annual gross rent > 200, renting is likely cheaper from a pure cash-flow perspective. In Madrid city center in 2026, average apartment prices run EUR 5,000-7,000/m², while rents run EUR 22-28/m²/month. For a 70 m² apartment: price ~EUR 420,000, annual rent ~EUR 22,176. Ratio = 420,000 / 22,176 = 18.9 (under 200×, purchase is relatively competitive). In tourist coastal areas (Costa del Sol, Canarias), ratios often exceed 25×, tilting toward renting or investment logic.

Common mistakes when taking a mortgage

Comparing only TIN, not TAE. TIN is the nominal rate; TAE includes all costs (origination fee, insurance bundled by the bank) and is the only valid basis for comparison between offers.
Taking the first offer. Comparing 3 banks plus a mortgage broker typically saves EUR 15,000-40,000 over 25 years on a EUR 200,000 loan.
Underestimating transaction costs. First-time buyers in Spain routinely underestimate the ITP bill and find themselves short at signing.
Signing at variable without modeling EURIBOR scenarios. Running the payment at EURIBOR + 2% (a historically plausible scenario) gives the stress-test version of affordability.
Not reading the amortization schedule. Understanding that 70% of the first 10 years of payments is interest (not principal) changes the calculus on early partial prepayment.

Refinancing decision framework 2026

Refinancing (subrogación in Spain) makes financial sense when two conditions are met simultaneously: the rate drop is at least 0.75 percentage points, and the remaining loan term is at least 10 years. Below either threshold, the closing costs typically exceed the present value of monthly savings.

Worked example: Existing loan EUR 180,000, remaining term 18 years, current rate 4.1%, new offer 3.2%. Monthly saving: old installment EUR 1,152 vs new EUR 1,047 = EUR 105/month. Total switching costs (early-repayment penalty 0.25% on variable, appraisal, notary, registry): approximately EUR 3,200. Breakeven = 3,200 ÷ 105 = 30.5 months. At 18 years remaining, the breakeven is reached in month 31 — the switch clearly pays. If the remaining term were only 6 years, total savings would be EUR 7,560 against EUR 3,200 of costs — still positive, but much tighter, and rate risk over a short horizon changes the calculus.

Complete Mortgage Guide

Methodology