function calculateRentalCashFlow() {
// 1. Get Inputs using var
var price = parseFloat(document.getElementById("rpcPurchasePrice").value) || 0;
var downPercent = parseFloat(document.getElementById("rpcDownPayment").value) || 0;
var interestRate = parseFloat(document.getElementById("rpcInterestRate").value) || 0;
var termYears = parseFloat(document.getElementById("rpcLoanTerm").value) || 0;
var closingCosts = parseFloat(document.getElementById("rpcClosingCosts").value) || 0;
var monthlyRent = parseFloat(document.getElementById("rpcMonthlyRent").value) || 0;
var annualTax = parseFloat(document.getElementById("rpcAnnualTax").value) || 0;
var annualIns = parseFloat(document.getElementById("rpcAnnualInsurance").value) || 0;
var monthlyHOA = parseFloat(document.getElementById("rpcMonthlyHOA").value) || 0;
var vacancyRate = parseFloat(document.getElementById("rpcVacancyRate").value) || 0;
var maintRate = parseFloat(document.getElementById("rpcMaintenanceRate").value) || 0;
// 2. Calculate Loan Details
var downPaymentAmount = price * (downPercent / 100);
var loanAmount = price – downPaymentAmount;
var totalCashInvested = downPaymentAmount + closingCosts;
// Mortgage Calculation (PI)
var monthlyRate = (interestRate / 100) / 12;
var numberOfPayments = termYears * 12;
var monthlyPI = 0;
if (interestRate === 0) {
monthlyPI = loanAmount / numberOfPayments;
} else {
monthlyPI = loanAmount * (monthlyRate * Math.pow(1 + monthlyRate, numberOfPayments)) / (Math.pow(1 + monthlyRate, numberOfPayments) – 1);
}
// Handle NaN if term is 0
if (!isFinite(monthlyPI)) monthlyPI = 0;
// 3. Calculate Expenses
var monthlyTax = annualTax / 12;
var monthlyIns = annualIns / 12;
var vacancyCost = monthlyRent * (vacancyRate / 100);
var maintCost = monthlyRent * (maintRate / 100);
var totalOperatingExpenses = monthlyTax + monthlyIns + monthlyHOA + vacancyCost + maintCost;
var totalMonthlyExpenses = totalOperatingExpenses + monthlyPI;
// 4. Calculate Metrics
var monthlyCashFlow = monthlyRent – totalMonthlyExpenses;
var annualCashFlow = monthlyCashFlow * 12;
var annualNOI = (monthlyRent * 12) – (totalOperatingExpenses * 12);
var cashOnCash = 0;
if (totalCashInvested > 0) {
cashOnCash = (annualCashFlow / totalCashInvested) * 100;
}
var capRate = 0;
if (price > 0) {
capRate = (annualNOI / price) * 100;
}
// 5. Update UI
// Helper function for currency formatting
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 2
});
document.getElementById("resIncome").innerHTML = formatter.format(monthlyRent);
document.getElementById("resMortgage").innerHTML = formatter.format(monthlyPI);
document.getElementById("resExpenses").innerHTML = formatter.format(totalMonthlyExpenses);
var cashFlowEl = document.getElementById("resCashFlow");
cashFlowEl.innerHTML = formatter.format(monthlyCashFlow);
if (monthlyCashFlow < 0) {
cashFlowEl.classList.add("negative");
} else {
cashFlowEl.classList.remove("negative");
}
document.getElementById("resCoC").innerHTML = cashOnCash.toFixed(2) + "%";
document.getElementById("resNOI").innerHTML = formatter.format(annualNOI);
document.getElementById("resCapRate").innerHTML = capRate.toFixed(2) + "%";
// Show results
document.getElementById("rpcResults").style.display = "block";
}
Understanding Rental Property Cash Flow
Calculating cash flow is the fundamental step in evaluating any real estate investment. Positive cash flow means the property generates more income than it costs to own and operate, providing you with passive income. Negative cash flow indicates the property is losing money every month.
How This Calculator Works
This Rental Property Cash Flow Calculator takes into account both the fixed costs of financing and variable operating expenses to give you a realistic picture of your investment's performance. It calculates three critical metrics:
Net Monthly Cash Flow: The actual dollar amount left in your pocket after paying the mortgage, taxes, insurance, and accounting for vacancy and maintenance reserves.
Cash on Cash Return (CoC): A percentage that measures the annual return on the actual cash you invested (down payment + closing costs). This is often considered the most important metric for investors.
Cap Rate (Capitalization Rate): This measures the property's natural rate of return independent of financing. It is calculated by dividing the Net Operating Income (NOI) by the purchase price.
Key Inputs Explained
To get accurate results, ensure you input realistic figures:
Vacancy Rate: No property is occupied 100% of the time. A standard conservative estimate is 5-8%, which accounts for turnover periods between tenants.
Maintenance/Repairs: Even new homes need repairs. Setting aside 5-10% of monthly rent helps cover future costs like HVAC repairs, painting, or plumbing issues.
Operating Expenses: Don't forget HOA fees, property taxes, and landlord insurance, as these significantly impact your bottom line.
What is a Good Cash on Cash Return?
While "good" is subjective, many real estate investors target a Cash on Cash return between 8% and 12%. However in high-appreciation markets, investors might accept a lower cash flow (4-6%) in exchange for long-term equity growth. Conversely, in stable markets with lower appreciation, investors often seek 10%+ returns.