function calculateRentalCashFlow() {
// 1. Get Inputs
var price = parseFloat(document.getElementById('rp_price').value) || 0;
var downPercent = parseFloat(document.getElementById('rp_down').value) || 0;
var interestRate = parseFloat(document.getElementById('rp_rate').value) || 0;
var termYears = parseFloat(document.getElementById('rp_term').value) || 0;
var monthlyRent = parseFloat(document.getElementById('rp_rent').value) || 0;
var vacancyPercent = parseFloat(document.getElementById('rp_vacancy').value) || 0;
var annualTax = parseFloat(document.getElementById('rp_tax').value) || 0;
var annualIns = parseFloat(document.getElementById('rp_insurance').value) || 0;
var annualRepairs = parseFloat(document.getElementById('rp_repairs').value) || 0;
var mgmtPercent = parseFloat(document.getElementById('rp_mgmt').value) || 0;
// 2. Calculate Mortgage (Principal & Interest)
var downPayment = price * (downPercent / 100);
var loanAmount = price – downPayment;
var monthlyMortgage = 0;
if (interestRate === 0) {
monthlyMortgage = loanAmount / (termYears * 12);
} else {
var monthlyRate = interestRate / 100 / 12;
var numPayments = termYears * 12;
if (numPayments > 0) {
monthlyMortgage = (loanAmount * monthlyRate) / (1 – Math.pow(1 + monthlyRate, -numPayments));
}
}
// 3. Calculate Monthly Expenses
var monthlyTax = annualTax / 12;
var monthlyIns = annualIns / 12;
var monthlyRepairs = annualRepairs / 12;
var vacancyCost = monthlyRent * (vacancyPercent / 100);
var mgmtCost = monthlyRent * (mgmtPercent / 100);
var totalOperatingExpenses = monthlyTax + monthlyIns + monthlyRepairs + vacancyCost + mgmtCost;
var totalMonthlyExpenses = totalOperatingExpenses + monthlyMortgage;
// 4. Calculate Returns
var monthlyCashFlow = monthlyRent – totalMonthlyExpenses;
var annualCashFlow = monthlyCashFlow * 12;
// Net Operating Income (NOI) = Income – Operating Expenses (Exclude Mortgage)
var annualNOI = (monthlyRent * 12) – (totalOperatingExpenses * 12);
// Cash on Cash Return = Annual Cash Flow / Total Cash Invested (assuming Down Payment is total investment for simplicity)
var cashOnCash = 0;
if (downPayment > 0) {
cashOnCash = (annualCashFlow / downPayment) * 100;
}
// Cap Rate = Annual NOI / Purchase Price
var capRate = 0;
if (price > 0) {
capRate = (annualNOI / price) * 100;
}
// 5. Display Results
var resultArea = document.getElementById('rp_results_area');
resultArea.style.display = 'block';
document.getElementById('res_mortgage').innerHTML = '$' + monthlyMortgage.toFixed(2);
document.getElementById('res_expenses').innerHTML = '$' + totalMonthlyExpenses.toFixed(2);
document.getElementById('res_noi_mo').innerHTML = '$' + (annualNOI / 12).toFixed(2);
// Handle coloring for positive/negative cash flow
var cashFlowEl = document.getElementById('res_cashflow_mo');
cashFlowEl.innerHTML = '$' + monthlyCashFlow.toFixed(2);
if (monthlyCashFlow < 0) {
cashFlowEl.className = 'rp-result-value rp-negative';
} else {
cashFlowEl.className = 'rp-result-value rp-highlight';
}
document.getElementById('res_cashflow_yr').innerHTML = '$' + annualCashFlow.toFixed(2);
document.getElementById('res_coc').innerHTML = cashOnCash.toFixed(2) + '%';
document.getElementById('res_cap').innerHTML = capRate.toFixed(2) + '%';
}
Understanding Rental Property Cash Flow Analysis
Investing in real estate is a powerful vehicle for wealth generation, but its success hinges on one critical metric: Cash Flow. This Rental Property Cash Flow Calculator is designed to help investors, both novice and experienced, accurately analyze the financial viability of a potential investment property. By factoring in not just the mortgage, but all operating expenses, vacancy rates, and management fees, you can determine if a property is an asset or a liability.
Why Cash Flow is King
Cash flow represents the net income from a real estate investment after mortgage payments and operating expenses have been made. Positive cash flow ensures that the property pays for itself and provides you with passive income. Negative cash flow, conversely, means you are paying out of pocket every month to hold the property—a risky strategy that relies solely on appreciation.
Key Metrics Explained
Net Operating Income (NOI): This is your total income minus operating expenses, excluding the mortgage. It is a pure measure of the property's efficiency.
Cash on Cash Return (CoC): This metric compares the annual cash flow to the total cash invested (down payment). It tells you how hard your money is working for you compared to other investment vehicles like stocks or bonds.
Cap Rate (Capitalization Rate): Calculated by dividing the NOI by the property's purchase price, the Cap Rate helps compare the profitability of different properties regardless of how they are financed.
How to Use This Calculator
To get the most accurate results, ensure you are realistic with your expense estimates:
Vacancy Rate: No property is occupied 100% of the time. A standard conservative estimate is 5% to 8% (roughly 2-4 weeks of vacancy per year).
Maintenance & Repairs: Budgeting 1% of the property value annually or 10% of the rental income is a prudent safeguard against unexpected costs like a broken water heater or roof repairs.
Management Fees: Even if you plan to self-manage, it is wise to factor in a 8-10% management fee. This ensures the deal still makes sense if you decide to hire a property manager later.
Interpreting Your Results
If your Cash on Cash Return is above 8-12%, you have likely found a solid investment. If the Monthly Cash Flow is negative, reconsider the purchase price or the financing terms. Successful investors use tools like this to remove emotion from the equation and make decisions based on hard data.