Principal: the portion of your payment that reduces the outstanding loan balance. In early payments on a 30-year mortgage at 7%, this is surprisingly small: on a $315,000 loan (at $350K purchase with 10% down), month 1 principal is approximately $260. Month 1 interest is $1,838. The first 7-8 years of a 30-year mortgage are almost entirely interest.

Interest: the lender's return on the outstanding balance. Calculated monthly: outstanding balance × (annual rate ÷ 12). On $315,000 at 7%: $315,000 × (0.07 ÷ 12) = $1,838 in month 1. Interest decreases incrementally each month as the balance amortizes.

Taxes: your lender collects 1/12 of your estimated annual property taxes each month and deposits them in an escrow account, paying the tax collector directly when bills are due. On a $350,000 home in a 1% effective-rate county: $3,500/year ÷ 12 = $292/month. This varies enormously by state and county.

Insurance: same escrow mechanism for homeowners insurance. At the national average of $2,000/year: $167/month. In Florida coastal markets at $7,200/year: $600/month. The insurance component is the most variable and market-specific.

PMI (Private Mortgage Insurance): required on conventional loans with under 20% down. Rate varies by LTV and credit score: typically 0.5-1.5% of the loan amount annually. On $315,000 loan at 0.6%: $1,890/year = $158/month. PMI cancels automatically at 78% original LTV; can be requested at 80% LTV. This is the most important reason a larger down payment reduces monthly cost beyond just the payment difference.

MIP (FHA Mortgage Insurance): required on FHA loans regardless of down payment. Two components: 1.75% upfront (financed) + 0.55% annual (monthly) for loans under 10% down. On $315,000 financed at 0.55%: $1,733/year = $144/month. MIP lasts the life of the loan if under 10% down (requires refinancing to eliminate).

HOA fees: not part of the mortgage but included in the DTI calculation for loan qualification. Range: $0 (no HOA) to $2,000+/month for luxury high-rises. HOA fees on a standard planned community: $200-$500/month. This is the component that most dramatically separates "mortgage payment" from "total housing cost."

$350,000 purchase, 10% down ($35,000), 7% 30-year conventional, $315,000 loan:

P&I: $2,097/month
Property taxes (1% annual estimate): $292/month
Homeowners insurance (national average): $167/month
PMI (0.6% annual): $158/month

Total PITI + PMI: $2,714/month

Add-ons depending on property type:
• HOA (basic community): + $250/month = $2,964 total
• HOA (full-amenity): + $400/month = $3,114 total

Florida coastal adjustment (insurance at $500/month):
• Replace $167 insurance with $500 = total rises by $333
• PITI + PMI in coastal FL: $3,047/month before HOA

The lesson: the "mortgage payment" advertised at $2,097/month is the P&I only. The real payment is $2,714-$3,100+ depending on location, insurance cost, and community type. Always model the full PITI-plus when calculating affordability.