function calculateCashFlow() {
// 1. Get Inputs
var price = parseFloat(document.getElementById('rp_price').value) || 0;
var downPercent = parseFloat(document.getElementById('rp_down').value) || 0;
var rate = parseFloat(document.getElementById('rp_rate').value) || 0;
var term = parseFloat(document.getElementById('rp_term').value) || 0;
var rent = parseFloat(document.getElementById('rp_rent').value) || 0;
var taxYearly = parseFloat(document.getElementById('rp_tax').value) || 0;
var insuranceYearly = parseFloat(document.getElementById('rp_insurance').value) || 0;
var hoaMonthly = parseFloat(document.getElementById('rp_hoa').value) || 0;
var vacancyPercent = parseFloat(document.getElementById('rp_vacancy').value) || 0;
var repairsPercent = parseFloat(document.getElementById('rp_repairs').value) || 0;
var managementPercent = parseFloat(document.getElementById('rp_management').value) || 0;
// 2. Logic: Mortgage
var downPayment = price * (downPercent / 100);
var loanAmount = price – downPayment;
var monthlyMortgage = 0;
if (loanAmount > 0 && rate > 0 && term > 0) {
var monthlyRate = (rate / 100) / 12;
var numPayments = term * 12;
monthlyMortgage = loanAmount * (monthlyRate * Math.pow(1 + monthlyRate, numPayments)) / (Math.pow(1 + monthlyRate, numPayments) – 1);
}
// 3. Logic: Expenses
var vacancyCost = rent * (vacancyPercent / 100);
var repairsCost = rent * (repairsPercent / 100);
var managementCost = rent * (managementPercent / 100);
var taxMonthly = taxYearly / 12;
var insuranceMonthly = insuranceYearly / 12;
var operatingExpenses = taxMonthly + insuranceMonthly + hoaMonthly + vacancyCost + repairsCost + managementCost;
var totalExpenses = operatingExpenses + monthlyMortgage;
// 4. Logic: Metrics
var cashFlow = rent – totalExpenses;
var annualCashFlow = cashFlow * 12;
var noiMonthly = rent – operatingExpenses;
var noiAnnual = noiMonthly * 12;
// Cash on Cash Return = Annual Pre-Tax Cash Flow / Total Cash Invested (Approximated as Down Payment for simplicity in this tool)
// Note: Closing costs usually add 2-5%, but we stick to inputs provided.
var cocReturn = 0;
if (downPayment > 0) {
cocReturn = (annualCashFlow / downPayment) * 100;
}
// Cap Rate = NOI / Price
var capRate = 0;
if (price > 0) {
capRate = (noiAnnual / price) * 100;
}
// 5. Display Results
document.getElementById('res_mortgage').innerText = '$' + monthlyMortgage.toFixed(2);
document.getElementById('res_expenses').innerText = '$' + totalExpenses.toFixed(2);
document.getElementById('res_noi').innerText = '$' + noiMonthly.toFixed(2);
var cfElement = document.getElementById('res_cashflow');
cfElement.innerText = '$' + cashFlow.toFixed(2);
if(cashFlow >= 0) {
cfElement.className = "rp-result-value rp-highlight";
} else {
cfElement.className = "rp-result-value rp-highlight rp-neg";
}
document.getElementById('res_coc').innerText = cocReturn.toFixed(2) + '%';
document.getElementById('res_cap').innerText = capRate.toFixed(2) + '%';
document.getElementById('rp_results').style.display = 'block';
}
Mastering Real Estate: Understanding Rental Property Cash Flow
Investing in rental properties is one of the most proven strategies for building long-term wealth. However, the difference between a successful investment and a financial burden often comes down to one metric: Cash Flow. This calculator helps investors analyze potential deals by accounting for all income and expenses associated with owning a rental property.
How is Cash Flow Calculated?
Cash flow is the net amount of money moving into or out of a business (or investment) at the center of the project. In real estate, the formula is:
Cash Flow = Total Rental Income – Total Expenses
Total expenses include not just the mortgage (principal and interest), but also taxes, insurance, vacancy provisions, repairs, capital expenditures (CapEx), homeowner association (HOA) fees, and property management fees. Ignoring "hidden" costs like vacancy rates or future repairs is the most common mistake new investors make.
Key Metrics Explained
Net Operating Income (NOI): This is your profitability before debt service (mortgage). It is calculated as Income minus Operating Expenses. It measures the potential of the asset itself, regardless of financing.
Cash on Cash Return (CoC): This measures the annual return on the actual cash you invested (Down Payment). A CoC of 8-12% is generally considered solid for rental properties, though this varies by market.
Cap Rate (Capitalization Rate): This metric helps compare the return of different properties independent of how they are financed. It is calculated as Annual NOI divided by the Purchase Price.
Tips for Improving Cash Flow
If your calculation shows negative or low cash flow, consider the following adjustments before walking away from a deal:
Increase Rent: Are current rents below market rates? Can minor cosmetic upgrades justify a higher price?
Reduce Vacancy: High vacancy kills returns. Ensure the property is in a desirable location and well-maintained to keep tenants longer.
Shop for Insurance and Financing: A lower interest rate or cheaper insurance premium directly boosts your bottom line.
Use the Rental Property Cash Flow Calculator above to run different scenarios. By adjusting the Purchase Price, Down Payment, or Interest Rate, you can determine exactly what offer price makes sense for your investment goals.