function calculateCashFlow() {
// Get Inputs
var price = parseFloat(document.getElementById('rpcPrice').value);
var down = parseFloat(document.getElementById('rpcDown').value);
var closing = parseFloat(document.getElementById('rpcClosing').value);
var rate = parseFloat(document.getElementById('rpcRate').value);
var term = parseFloat(document.getElementById('rpcTerm').value);
var rent = parseFloat(document.getElementById('rpcRent').value);
var tax = parseFloat(document.getElementById('rpcTax').value);
var ins = parseFloat(document.getElementById('rpcIns').value);
var hoa = parseFloat(document.getElementById('rpcHoa').value);
var maint = parseFloat(document.getElementById('rpcMaint').value);
// Validation
if (isNaN(price) || isNaN(down) || isNaN(rate) || isNaN(term) || isNaN(rent) || isNaN(tax) || isNaN(ins)) {
alert("Please fill out all fields with valid numbers.");
return;
}
// Mortgage Calculation
var loanAmount = price – down;
var monthlyRate = (rate / 100) / 12;
var numPayments = term * 12;
var monthlyMortgage = 0;
if (rate > 0) {
monthlyMortgage = loanAmount * (monthlyRate * Math.pow(1 + monthlyRate, numPayments)) / (Math.pow(1 + monthlyRate, numPayments) – 1);
} else {
monthlyMortgage = loanAmount / numPayments;
}
// Monthly Expenses Calculation
var monthlyTax = tax / 12;
var monthlyIns = ins / 12;
var monthlyMaint = maint / 12;
// Fix NaN for optional HOA if empty
if (isNaN(hoa)) hoa = 0;
var totalMonthlyExpenses = monthlyMortgage + monthlyTax + monthlyIns + hoa + monthlyMaint;
// Cash Flow
var monthlyCashFlow = rent – totalMonthlyExpenses;
var annualCashFlow = monthlyCashFlow * 12;
// Cash on Cash Return
// Total Cash Invested = Down Payment + Closing Costs
var totalInvested = down + closing;
var cocReturn = 0;
if (totalInvested > 0) {
cocReturn = (annualCashFlow / totalInvested) * 100;
}
// Display Results
document.getElementById('rpcResults').style.display = 'block';
document.getElementById('resMortgage').innerText = "$" + monthlyMortgage.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resExpenses').innerText = "$" + totalMonthlyExpenses.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
var flowEl = document.getElementById('resCashFlow');
flowEl.innerText = "$" + monthlyCashFlow.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
// Color coding for cash flow
if (monthlyCashFlow >= 0) {
flowEl.style.color = "#27ae60";
} else {
flowEl.style.color = "#c0392b";
}
document.getElementById('resCoc').innerText = cocReturn.toFixed(2) + "%";
}
Mastering Your Rental Property Investment
Investing in real estate is one of the most reliable ways to build wealth, but understanding the numbers is crucial. This Rental Property Cash Flow Calculator helps investors analyze potential deals by breaking down income, expenses, and returns.
Why Cash Flow Matters
Cash flow is the net amount of money moving into or out of your rental business after all expenses are paid. Positive cash flow means the property is generating income for you every month, while negative cash flow means you are paying out of pocket to hold the asset. For long-term sustainability, investors typically prioritize properties with positive monthly cash flow.
Understanding the Metrics
NOI (Net Operating Income): This is your annual rental income minus all operating expenses (taxes, insurance, maintenance, HOA) but excluding mortgage payments.
Cash on Cash Return (CoC): This is arguably the most important metric for ROI. It measures the annual cash income earned on the cash you actually invested (Down Payment + Closing Costs). A CoC return of 8-12% is often considered a solid benchmark for rental properties.
Cap Rate: While not calculated directly above, the Capitalization Rate compares the NOI to the property price. It is useful for comparing the raw potential of different properties regardless of financing.
How to Use This Calculator
Purchase Info: Enter the price of the property and your financing details. Don't forget closing costs, which typically range from 2% to 5% of the purchase price.
Income: Input the expected monthly rent. Be realistic—check local comps (comparable properties) to ensure your estimate is accurate.
Expenses: Account for all costs. "Maintenance" should be an estimate (often 1% of property value per year) to cover future repairs like roof replacements or HVAC issues.
Tips for Improving Cash Flow
If your calculation shows negative or low cash flow, consider these adjustments: increasing the down payment to lower the mortgage, shopping for a lower insurance rate, or looking for ways to add value to the property to justify higher rent (e.g., adding in-unit laundry or modernizing the kitchen).