{
    "title": "Mortgage Calculator Input Accuracy Report",
    "updated": "2026-08-06",
    "methodology": "The report maps common mortgage calculator fields to their role in principal-and-interest, monthly housing, or upfront cash estimates.",
    "limitations": "Actual loan offers, taxes, insurance, fees, underwriting, and eligibility vary. This is not a lending decision.",
    "columns": [
        "Input",
        "Include?",
        "Common mistake",
        "Effect"
    ],
    "rows": [
        [
            "Home price",
            "Yes",
            "Using loan amount instead",
            "Changes down payment and affordability"
        ],
        [
            "Down payment",
            "Yes",
            "Ignoring closing cash needs",
            "Changes principal and cash required"
        ],
        [
            "Interest rate",
            "Yes",
            "Using APR as note rate without context",
            "Changes payment estimate"
        ],
        [
            "Loan term",
            "Yes",
            "Assuming every loan is 30 years",
            "Changes amortization"
        ],
        [
            "Property tax",
            "Usually",
            "Using a national average",
            "Can materially change monthly cost"
        ],
        [
            "Homeowners insurance",
            "Usually",
            "Omitting it",
            "Understates housing cost"
        ],
        [
            "Mortgage insurance",
            "When applicable",
            "Assuming it never applies",
            "Understates cost"
        ],
        [
            "HOA dues",
            "When applicable",
            "Leaving association fees out",
            "Understates recurring cost"
        ],
        [
            "Closing costs",
            "Separate cash estimate",
            "Adding every fee into payment",
            "Confuses upfront and monthly costs"
        ],
        [
            "Points/credits",
            "When selected",
            "Ignoring rate tradeoff",
            "Changes cash and rate"
        ],
        [
            "Start date",
            "For schedule",
            "Assuming payment begins immediately",
            "Affects timeline"
        ],
        [
            "Extra payment",
            "Optional",
            "Treating it as required payment",
            "Changes payoff projection"
        ],
        [
            "Maintenance",
            "Budget separately",
            "Calling mortgage payment total ownership cost",
            "Understates ownership cost"
        ],
        [
            "Utilities",
            "Budget separately",
            "Assuming included",
            "Understates household budget"
        ]
    ]
}