function calculateRentalCashFlow() {
// 1. Get Values
var price = parseFloat(document.getElementById('purchasePrice').value) || 0;
var downPercent = parseFloat(document.getElementById('downPayment').value) || 0;
var interestRate = parseFloat(document.getElementById('interestRate').value) || 0;
var termYears = parseInt(document.getElementById('loanTerm').value) || 30;
var rawRent = parseFloat(document.getElementById('monthlyRent').value) || 0;
var otherIncome = parseFloat(document.getElementById('otherIncome').value) || 0;
var vacancyPercent = parseFloat(document.getElementById('vacancyRate').value) || 0;
var yearlyTax = parseFloat(document.getElementById('propertyTax').value) || 0;
var yearlyIns = parseFloat(document.getElementById('insurance').value) || 0;
var monthlyHOA = parseFloat(document.getElementById('hoaFees').value) || 0;
var maintPercent = parseFloat(document.getElementById('maintenance').value) || 0;
var mgmtPercent = parseFloat(document.getElementById('managementFee').value) || 0;
var capexPercent = parseFloat(document.getElementById('capex').value) || 0;
// 2. Loan Calculations
var downPaymentAmount = price * (downPercent / 100);
var loanAmount = price – downPaymentAmount;
var monthlyRate = (interestRate / 100) / 12;
var numPayments = termYears * 12;
var monthlyMortgage = 0;
if (loanAmount > 0 && monthlyRate > 0) {
monthlyMortgage = loanAmount * (monthlyRate * Math.pow(1 + monthlyRate, numPayments)) / (Math.pow(1 + monthlyRate, numPayments) – 1);
} else if (loanAmount > 0 && monthlyRate === 0) {
monthlyMortgage = loanAmount / numPayments;
}
// 3. Income Calculations (Adjusted for Vacancy)
var vacancyLoss = rawRent * (vacancyPercent / 100);
var effectiveGrossIncome = (rawRent + otherIncome) – vacancyLoss;
// 4. Expense Calculations
var monthlyTax = yearlyTax / 12;
var monthlyIns = yearlyIns / 12;
var monthlyMaint = rawRent * (maintPercent / 100);
var monthlyMgmt = rawRent * (mgmtPercent / 100);
var monthlyCapex = rawRent * (capexPercent / 100);
var totalOperatingExpenses = monthlyTax + monthlyIns + monthlyHOA + monthlyMaint + monthlyMgmt + monthlyCapex;
// 5. Profitability Calculations
var monthlyCashFlow = effectiveGrossIncome – totalOperatingExpenses – monthlyMortgage;
var annualCashFlow = monthlyCashFlow * 12;
var annualNOI = (effectiveGrossIncome – totalOperatingExpenses) * 12;
// Initial Cash Investment (Downpayment + Closing Costs roughly 3% est + Rehab costs 0)
// For simplicity, we calculate Cash on Cash based on Down Payment only, though users should add closing costs mentally.
var totalCashInvested = downPaymentAmount;
var capRate = 0;
if (price > 0) {
capRate = (annualNOI / price) * 100;
}
var cashOnCash = 0;
if (totalCashInvested > 0) {
cashOnCash = (annualCashFlow / totalCashInvested) * 100;
}
// 6. Format and Display
var formatter = new Intl.NumberFormat('en-US', { style: 'currency', currency: 'USD' });
document.getElementById('resIncome').innerText = formatter.format(effectiveGrossIncome);
document.getElementById('resExpenses').innerText = formatter.format(totalOperatingExpenses);
document.getElementById('resMortgage').innerText = formatter.format(monthlyMortgage);
var cashFlowEl = document.getElementById('resCashFlow');
cashFlowEl.innerText = formatter.format(monthlyCashFlow);
if(monthlyCashFlow >= 0) {
cashFlowEl.className = "rp-result-value rp-highlight-positive";
} else {
cashFlowEl.className = "rp-result-value rp-highlight-negative";
}
document.getElementById('resNOI').innerText = formatter.format(annualNOI);
document.getElementById('resCapRate').innerText = capRate.toFixed(2) + "%";
var cocEl = document.getElementById('resCoC');
cocEl.innerText = cashOnCash.toFixed(2) + "%";
if(cashOnCash >= 0) {
cocEl.className = "rp-result-value rp-highlight-positive";
} else {
cocEl.className = "rp-result-value rp-highlight-negative";
}
document.getElementById('resultsArea').style.display = 'block';
}
Understanding Real Estate Cash Flow
Investing in rental properties is a proven strategy for building long-term wealth, but success hinges on the numbers. This Rental Property Cash Flow Calculator helps investors determine if a potential property will generate income or drain resources. By analyzing the income against operating expenses and debt service, you can calculate the net profit of a real estate investment.
Key Metrics Explained
1. Net Operating Income (NOI)
NOI is one of the most critical figures in real estate. It represents the annual income generated by the property after deducting all operating expenses (like taxes, insurance, and maintenance) but before deducting mortgage payments. A positive NOI indicates that the property operations are profitable.
2. Cash Flow
While NOI looks at operations, Cash Flow looks at your pocket. It is calculated by subtracting your debt service (mortgage payments) from the NOI. Formula:Income – Expenses – Mortgage = Cash Flow.
Positive cash flow means the property pays for itself and provides you with passive income. Negative cash flow means you are paying monthly to hold the asset.
3. Cash on Cash Return (CoC)
This metric measures the return on the actual cash you invested (down payment), rather than the total value of the property. It is essentially the interest rate on your money. A CoC return of 8-12% is often considered a solid benchmark for rental investors, though this varies by market.
4. Cap Rate (Capitalization Rate)
The Cap Rate measures a property's natural rate of return assuming it was bought with all cash. It allows you to compare properties of different sizes and prices apples-to-apples. Higher Cap Rates generally imply higher risk or higher potential return, while lower Cap Rates are associated with safer, stabilized assets in prime locations.
How to Improve Rental Cash Flow
Increase Rent: Keeping rents at market value is the fastest way to boost NOI.
Reduce Vacancy: High turnover kills returns. Screening tenants rigorously can ensure long-term occupancy.
Challenge Property Taxes: If your assessment is too high compared to comparable properties, filing an appeal can lower your fixed costs.
Refinance: Securing a lower interest rate or extending the loan term can significantly reduce monthly mortgage payments, immediately increasing cash flow.
Use this calculator to run scenarios on different properties. Adjust the purchase price, down payment, and rent estimates to see how sensitive your returns are to market changes.