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How to Calculate Rental Property Cash Flow
Understanding the true profitability of a real estate investment requires more than just subtracting the mortgage from the rent. To determine if a property is a "good deal," you must account for "hidden" costs like vacancy, capital expenditures, and management fees.
The Core Formula
The standard formula for monthly cash flow is:
Cash Flow = Gross Rent – (Mortgage + Taxes + Insurance + Maintenance + Vacancy + Management)
Key Real Estate Metrics Explained
- Cap Rate (Capitalization Rate): This measures the property's natural rate of return without considering financing. It is calculated by dividing the Net Operating Income (NOI) by the purchase price.
- Cash-on-Cash (CoC) Return: This is the most important metric for many investors. It measures the annual cash flow relative to the actual cash you invested (down payment and closing costs).
- Vacancy Allowance: No property is occupied 100% of the time. Smart investors set aside 5-10% of gross rent to cover turnover periods.
- CapEx (Capital Expenditures): This covers big-ticket items like a new roof or HVAC system. Setting aside 5-10% monthly prevents these repairs from ruining your yearly profit.
Example Calculation
Suppose you buy a property for $200,000 with 20% down ($40,000). Your mortgage is $1,000. Rent is $2,000.
Monthly Expenses:
– Taxes/Insurance: $300
– Maintenance (10%): $200
– Vacancy (5%): $100
Total Expenses: $1,600.
Net Monthly Cash Flow: $400 ($2,000 – $1,600).
function calculateRentalCashFlow() {
var price = parseFloat(document.getElementById('purchasePrice').value);
var downPercent = parseFloat(document.getElementById('downPaymentPercent').value) / 100;
var interest = parseFloat(document.getElementById('interestRate').value) / 100 / 12;
var term = parseFloat(document.getElementById('loanTerm').value) * 12;
var rent = parseFloat(document.getElementById('monthlyRent').value);
var tax = parseFloat(document.getElementById('propertyTax').value);
var insurance = parseFloat(document.getElementById('insurance').value);
var maintenance = parseFloat(document.getElementById('maintenancePercent').value) / 100;
var vacancy = parseFloat(document.getElementById('vacancyPercent').value) / 100;
var mgmt = parseFloat(document.getElementById('mgmtPercent').value) / 100;
if (isNaN(price) || isNaN(rent)) {
alert("Please enter valid property details.");
return;
}
// Loan Logic
var downPaymentAmt = price * downPercent;
var loanAmt = price – downPaymentAmt;
var mortgage = 0;
if (interest > 0) {
mortgage = (loanAmt * interest * Math.pow(1 + interest, term)) / (Math.pow(1 + interest, term) – 1);
} else {
mortgage = loanAmt / term;
}
// Variable Expenses
var maintAmt = rent * maintenance;
var vacancyAmt = rent * vacancy;
var mgmtAmt = rent * mgmt;
var totalMonthlyExpenses = mortgage + tax + insurance + maintAmt + vacancyAmt + mgmtAmt;
// Cash Flow
var monthlyCashFlow = rent – totalMonthlyExpenses;
// NOI (Annual) – Mortgage is not included in NOI
var monthlyNOI = rent – (tax + insurance + maintAmt + vacancyAmt + mgmtAmt);
var annualNOI = monthlyNOI * 12;
// ROI Metrics
var capRate = (annualNOI / price) * 100;
var cocReturn = ((monthlyCashFlow * 12) / downPaymentAmt) * 100;
// Display
document.getElementById('results').style.display = 'block';
document.getElementById('resMortgage').innerText = '$' + mortgage.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resExpenses').innerText = '$' + totalMonthlyExpenses.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
var cashFlowEl = document.getElementById('resCashFlow');
cashFlowEl.innerText = '$' + monthlyCashFlow.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
if (monthlyCashFlow < 0) {
cashFlowEl.className = 'result-value negative-value';
} else {
cashFlowEl.className = 'result-value';
}
document.getElementById('resCapRate').innerText = capRate.toFixed(2) + '%';
document.getElementById('resCoC').innerText = cocReturn.toFixed(2) + '%';
// Scroll to results on mobile
if(window.innerWidth < 600) {
document.getElementById('results').scrollIntoView({behavior: 'smooth'});
}
}