MortgageUtils 1.0.0

MortgageUtils

A .NET library for US mortgage calculations and educational borrower screening.

Built by OurNetHelps.com, mortgage technology tools for US mortgage brokers.

Educational use only. This library provides simplified calculation utilities and screening estimates. It does not determine mortgage approval, eligibility, or underwriting outcomes. Actual underwriting requirements vary by lender, loan program, automated underwriting system, and borrower circumstances.

Installation

dotnet add package MortgageUtils

Usage

DTI Calculation

using MortgageUtils;

// Conventional DTI (28% front-end / 45% back-end modeled thresholds)
var dti = MortgageCalculator.CalculateDTI(
    grossMonthlyIncome: 6000,
    monthlyHousingCost: 1500,
    otherMonthlyDebts: 600
);

Console.WriteLine($"Front-end DTI: {dti.FrontEndDTI:F1}%");   // 25.0%
Console.WriteLine($"Back-end DTI: {dti.BackEndDTI:F1}%");     // 35.0%
Console.WriteLine($"Front-end status: {dti.FrontEndStatus}"); // Good
Console.WriteLine($"Back-end status: {dti.BackEndStatus}");   // Good

// FHA-specific status labels (31% / 50% modeled thresholds)
var dtiFHA = MortgageCalculator.CalculateDTIForLoanType(
    grossMonthlyIncome: 6000,
    monthlyHousingCost: 1500,
    otherMonthlyDebts: 600,
    loanType: LoanType.FHA
);
Console.WriteLine($"FHA back-end status: {dtiFHA.BackEndStatus}");

LTV Calculation

// Conventional LTV
var ltv = MortgageCalculator.CalculateLTV(
    propertyValue: 350000,
    loanAmount: 280000,
    loanType: LoanType.Conventional
);

Console.WriteLine($"LTV: {ltv.Ratio:F1}%");                        // 80.0%
Console.WriteLine($"Mortgage insurance: {ltv.MortgageInsurance}"); // None

// FHA carries MIP (this library identifies the type only; MIP amounts and duration
// depend on loan term, LTV, and base loan amount , not calculated here)
var ltvFHA = MortgageCalculator.CalculateLTV(350000, 280000, LoanType.FHA);
Console.WriteLine($"FHA insurance: {ltvFHA.MortgageInsurance}"); // FHA_MIP

// VA has no conventional PMI
var ltvVA = MortgageCalculator.CalculateLTV(350000, 350000, LoanType.VA);
Console.WriteLine($"VA insurance: {ltvVA.MortgageInsurance}"); // None

Monthly Payment

var payment = MortgageCalculator.CalculateMonthlyPayment(
    loanAmount: 280000,
    annualInterestRate: 6.5,
    termYears: 30
);
Console.WriteLine($"Monthly Payment: ${payment:F2}"); // $1,770.04

// Zero percent interest rate supported
var zeroRate = MortgageCalculator.CalculateMonthlyPayment(120000, 0, 10);
Console.WriteLine($"0% interest payment: ${zeroRate:F2}"); // $1,000.00

Borrower Screening

var screening = MortgageCalculator.ScreenBorrower(
    grossMonthlyIncome: 6000,
    monthlyHousingCost: 1500,
    otherMonthlyDebts: 600,
    propertyValue: 350000,
    loanAmount: 280000,
    creditScore: 720,
    loanType: LoanType.Conventional
);

Console.WriteLine($"Meets modeled criteria: {screening.MeetsModeledCriteria}");
foreach (var note in screening.Notes)
    Console.WriteLine($"  - {note}");

Modeled Screening Thresholds

These are the simplified values used by this library. They are not universal underwriting rules.

*VA values are this library's own modeled screening parameters. VA has no official credit score minimum and no official front-end DTI limit. VA underwriting considers residual income and other factors not modeled here.

Conventional and FHA thresholds are simplified. Actual criteria vary by automated underwriting system, lender overlays, and compensating factors.

License

MIT License. Copyright 2026 Sanjeev Kumar, OurNetHelps.com.