/* Critical CSS for layout and styling */
.rp-calculator-wrapper {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
max-width: 800px;
margin: 20px auto;
border: 1px solid #e0e0e0;
border-radius: 8px;
background: #fff;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
padding: 0;
overflow: hidden;
}
.rp-calc-header {
background: #2c3e50;
color: #fff;
padding: 20px;
text-align: center;
}
.rp-calc-header h2 {
margin: 0;
font-size: 24px;
}
.rp-calc-body {
padding: 25px;
display: flex;
flex-wrap: wrap;
gap: 20px;
}
.rp-input-group {
flex: 1 1 300px;
display: flex;
flex-direction: column;
gap: 15px;
}
.rp-input-field {
display: flex;
flex-direction: column;
}
.rp-input-field label {
font-weight: 600;
font-size: 14px;
color: #333;
margin-bottom: 5px;
}
.rp-input-field input, .rp-input-field select {
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 16px;
}
.rp-input-field input:focus {
border-color: #2c3e50;
outline: none;
}
.rp-calc-btn {
width: 100%;
background: #27ae60;
color: white;
border: none;
padding: 15px;
font-size: 18px;
font-weight: bold;
border-radius: 4px;
cursor: pointer;
margin-top: 10px;
transition: background 0.2s;
}
.rp-calc-btn:hover {
background: #219150;
}
.rp-results-area {
flex: 1 1 300px;
background: #f8f9fa;
border-radius: 6px;
padding: 20px;
border: 1px solid #e9ecef;
}
.rp-result-row {
display: flex;
justify-content: space-between;
margin-bottom: 12px;
padding-bottom: 12px;
border-bottom: 1px solid #e0e0e0;
font-size: 15px;
}
.rp-result-row.total {
border-bottom: none;
border-top: 2px solid #ccc;
padding-top: 15px;
font-weight: bold;
font-size: 18px;
color: #2c3e50;
}
.rp-result-row.positive { color: #27ae60; }
.rp-result-row.negative { color: #c0392b; }
/* Article Styling */
.rp-article-content {
max-width: 800px;
margin: 40px auto;
padding: 0 15px;
font-family: inherit;
line-height: 1.6;
color: #333;
}
.rp-article-content h2 { color: #2c3e50; border-bottom: 2px solid #eee; padding-bottom: 10px; margin-top: 30px;}
.rp-article-content h3 { color: #34495e; margin-top: 25px; }
.rp-article-content p { margin-bottom: 15px; }
.rp-article-content ul { margin-bottom: 15px; padding-left: 20px; }
.rp-article-content li { margin-bottom: 8px; }
@media (max-width: 600px) {
.rp-calc-body { flex-direction: column; }
}
Financial Performance
Monthly P&I Payment:
$0.00
Monthly Taxes & Ins:
$0.00
Other Monthly Exp:
$0.00
Total Monthly Outflow:
$0.00
Net Monthly Cash Flow:
$0.00
Cash on Cash Return:
0.00%
Cap Rate:
0.00%
*Estimates only. Does not include vacancy rates or closing costs unless added to expenses.
function calculateCashFlow() {
// 1. Get DOM elements
var purchasePriceInput = document.getElementById("purchasePrice");
var downPaymentInput = document.getElementById("downPayment");
var interestRateInput = document.getElementById("interestRate");
var loanTermInput = document.getElementById("loanTerm");
var monthlyRentInput = document.getElementById("monthlyRent");
var propertyTaxInput = document.getElementById("propertyTax");
var insuranceInput = document.getElementById("insurance");
var otherExpensesInput = document.getElementById("otherExpenses");
// 2. Parse values
var price = parseFloat(purchasePriceInput.value) || 0;
var down = parseFloat(downPaymentInput.value) || 0;
var rate = parseFloat(interestRateInput.value) || 0;
var years = parseFloat(loanTermInput.value) || 30;
var rent = parseFloat(monthlyRentInput.value) || 0;
var taxYear = parseFloat(propertyTaxInput.value) || 0;
var insYear = parseFloat(insuranceInput.value) || 0;
var otherMo = parseFloat(otherExpensesInput.value) || 0;
// 3. Logic: Mortgage Calculation (Principal & Interest)
var loanAmount = price – down;
var monthlyRate = (rate / 100) / 12;
var numberOfPayments = years * 12;
var monthlyPI = 0;
if (rate > 0 && loanAmount > 0) {
// Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
var x = Math.pow(1 + monthlyRate, numberOfPayments);
monthlyPI = loanAmount * ((monthlyRate * x) / (x – 1));
} else if (loanAmount > 0) {
monthlyPI = loanAmount / numberOfPayments;
}
// 4. Logic: Expenses
var monthlyTax = taxYear / 12;
var monthlyIns = insYear / 12;
var totalMonthlyFixedExpenses = monthlyTax + monthlyIns + otherMo;
var totalMonthlyOutflow = monthlyPI + totalMonthlyFixedExpenses;
// 5. Logic: Cash Flow
var cashFlow = rent – totalMonthlyOutflow;
// 6. Logic: ROI Metrics
// Annual Cash Flow
var annualCashFlow = cashFlow * 12;
// Cash on Cash Return = Annual Pre-Tax Cash Flow / Total Cash Invested (Down Payment)
// Note: Simplification assumes closing costs are zero or part of down payment for this calc
var cashOnCash = 0;
if (down > 0) {
cashOnCash = (annualCashFlow / down) * 100;
}
// Cap Rate = Net Operating Income (NOI) / Current Market Value
// NOI = Annual Income – Operating Expenses (Excluding Mortgage)
var annualOperatingExpenses = (totalMonthlyFixedExpenses * 12);
var noi = (rent * 12) – annualOperatingExpenses;
var capRate = 0;
if (price > 0) {
capRate = (noi / price) * 100;
}
// 7. Update DOM
document.getElementById("resPrincipalInterest").innerText = "$" + monthlyPI.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("resTaxIns").innerText = "$" + (monthlyTax + monthlyIns).toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("resOther").innerText = "$" + otherMo.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("resTotalExpenses").innerText = "$" + totalMonthlyOutflow.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
var cfElement = document.getElementById("resCashFlow");
cfElement.innerText = "$" + cashFlow.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
// Style output color based on positivity
if(cashFlow > 0) {
cfElement.style.color = "#27ae60";
} else if (cashFlow < 0) {
cfElement.style.color = "#c0392b";
} else {
cfElement.style.color = "#2c3e50";
}
document.getElementById("resCoC").innerText = cashOnCash.toFixed(2) + "%";
document.getElementById("resCapRate").innerText = capRate.toFixed(2) + "%";
}
// Run once on load to populate defaults
window.onload = function() {
calculateCashFlow();
};
Understanding Rental Property Cash Flow
Investing in real estate is one of the most reliable ways to build wealth, but simply buying a property doesn't guarantee a profit. The most critical metric for any buy-and-hold investor is Cash Flow. This calculator helps you analyze a potential rental property to determine if it will generate positive monthly income after all expenses are paid.
What is Positive Cash Flow?
Positive cash flow occurs when your property's gross monthly rental income exceeds the total of your mortgage payments and operating expenses. Operating expenses include property taxes, insurance, homeowners association (HOA) fees, repairs, and capital expenditures (CapEx). A property with positive cash flow puts money in your pocket every month, providing a safety net against vacancies and maintenance issues.
Key Metrics Explained
- NOI (Net Operating Income): This is your annual income minus operating expenses, excluding the mortgage payment. It measures the property's profitability purely as an asset, regardless of financing.
- Cash on Cash Return (CoC): This measures the annual return on the actual cash you invested (down payment + closing costs). A CoC return of 8-12% is generally considered good by most investors.
- Cap Rate: Calculated by dividing the NOI by the property's purchase price. This helps compare the profitability of similar properties in the same market, regardless of how they were financed.
The 1% Rule
When quickly screening properties, many investors use the "1% Rule." This rule suggests that a property's monthly rent should be at least 1% of the purchase price. For example, a $200,000 home should rent for at least $2,000/month. While not a hard rule, properties that meet this criteria are more likely to generate positive cash flow.
Hidden Costs to Watch For
Many new investors fail because they underestimate expenses. When using this calculator, ensure you account for "invisible" costs like vacancy rates (typically 5-8% of rent), property management fees (8-10%), and long-term maintenance (replacing a roof or HVAC system). It is always safer to overestimate expenses than to overestimate income.