function calculateRentalROI() {
// Get Inputs
var price = parseFloat(document.getElementById("rpcPrice").value);
var closingCosts = parseFloat(document.getElementById("rpcClosingCosts").value);
var downPaymentPercent = parseFloat(document.getElementById("rpcDownPayment").value);
var interestRate = parseFloat(document.getElementById("rpcInterest").value);
var loanTerm = parseFloat(document.getElementById("rpcTerm").value);
var rent = parseFloat(document.getElementById("rpcRent").value);
var expenses = parseFloat(document.getElementById("rpcExpenses").value);
// Validation
if (isNaN(price) || isNaN(rent) || isNaN(expenses)) {
alert("Please enter valid numbers for Price, Rent, and Expenses.");
return;
}
// Set defaults for optional fields if empty to avoid NaN
if (isNaN(closingCosts)) closingCosts = 0;
if (isNaN(downPaymentPercent)) downPaymentPercent = 20;
if (isNaN(interestRate)) interestRate = 0;
if (isNaN(loanTerm)) loanTerm = 30;
// Calculations
var downPaymentAmount = price * (downPaymentPercent / 100);
var loanAmount = price – downPaymentAmount;
var totalCashInvested = downPaymentAmount + closingCosts;
// Mortgage Calculation (M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ])
var monthlyMortgage = 0;
if (interestRate > 0 && loanTerm > 0) {
var monthlyRate = (interestRate / 100) / 12;
var numberOfPayments = loanTerm * 12;
monthlyMortgage = loanAmount * (monthlyRate * Math.pow(1 + monthlyRate, numberOfPayments)) / (Math.pow(1 + monthlyRate, numberOfPayments) – 1);
} else {
// If 0 interest or cash purchase logic (though term is usually required)
if (loanTerm > 0) {
monthlyMortgage = loanAmount / (loanTerm * 12);
} else {
monthlyMortgage = 0; // Assuming full cash or invalid term
}
}
var totalMonthlyOutflow = monthlyMortgage + expenses;
var monthlyCashFlow = rent – totalMonthlyOutflow;
var annualCashFlow = monthlyCashFlow * 12;
// Cash on Cash Return = Annual Pre-Tax Cash Flow / Total Cash Invested
var cocReturn = 0;
if (totalCashInvested > 0) {
cocReturn = (annualCashFlow / totalCashInvested) * 100;
}
// Display Results
document.getElementById("rpcResults").style.display = "block";
document.getElementById("rpcResMortgage").innerText = formatCurrency(monthlyMortgage);
document.getElementById("rpcResTotalCost").innerText = formatCurrency(totalMonthlyOutflow);
var cashFlowEl = document.getElementById("rpcResCashFlow");
cashFlowEl.innerText = formatCurrency(monthlyCashFlow);
colorResult(cashFlowEl, monthlyCashFlow);
var annualEl = document.getElementById("rpcResAnnualCashFlow");
annualEl.innerText = formatCurrency(annualCashFlow);
colorResult(annualEl, annualCashFlow);
var cocEl = document.getElementById("rpcResCoC");
cocEl.innerText = cocReturn.toFixed(2) + "%";
colorResult(cocEl, cocReturn);
}
function formatCurrency(num) {
return "$" + num.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,');
}
function colorResult(element, value) {
element.classList.remove("positive", "negative");
if (value >= 0) {
element.classList.add("positive");
} else {
element.classList.add("negative");
}
}
Understanding Rental Property Cash Flow
Investing in real estate is one of the most reliable ways to build wealth, but the difference between a successful investment and a financial burden often comes down to one metric: Cash Flow. This Rental Property Cash Flow Calculator is designed to help investors quickly analyze the profitability of a potential purchase.
What is Cash Flow?
Cash flow represents the net amount of money moving in and out of your rental business. Positive cash flow means your property generates more income than it costs to operate, putting money into your pocket every month. Negative cash flow means you are losing money to keep the property running.
The basic formula used in this calculator is:
Income: Monthly Rent.
Expenses: Mortgage (Principal & Interest), Taxes, Insurance, HOA Fees, Repairs, and Vacancy reserves.
Cash Flow = Income – Expenses.
Why Cash on Cash Return (CoC) Matters
While monthly cash flow tells you the dollar amount you earn, the Cash on Cash Return tells you how hard your money is working. It measures the annual return on the actual cash you invested (down payment + closing costs), rather than the total loan amount.
For example, if you invest $50,000 cash to buy a property and it generates $5,000 in annual cash flow, your CoC return is 10%. This metric allows you to compare real estate investments against other vehicles like stocks or bonds.
How to Use This Calculator
Purchase Information: Enter the price of the property and your estimated closing costs (typically 2-5% of the price).
Financing Details: Input your down payment percentage, interest rate, and loan term. If you are paying cash, set the interest rate to 0.
Income & Expenses: Enter the expected monthly rent. For expenses, be sure to sum up property taxes, insurance, HOA fees, and a budget for maintenance (often estimated at 1% of property value per year).
Analyze: Hit calculate to see your estimated monthly P&I, total costs, net cash flow, and ROI.
What is a good Cash on Cash return?
Most investors aim for a CoC return between 8% and 12%, though this varies by market. In high-appreciation markets, investors might accept lower cash flow returns (4-6%), while in stable cash-flow markets, they may seek 15%+.
Should I include vacancy rates in expenses?
Yes. Even if a property is currently rented, it will not be occupied 100% of the time forever. A standard conservative estimate is to allocate 5% to 8% of the monthly rent toward a vacancy reserve.