Understanding ROI, cash flow, and rental property calculations
The Invest Nest's rental property calculator helps you analyze the financial picture of a buy-and-hold deal before you make an offer. This article walks through what each input means, what the outputs tell you, and how to interpret the numbers.
The calculator is built for buy-and-hold rentals. It's not designed for fix-and-flip projects, where the math works very differently.
How to access the calculator
Open any property by clicking it on the map or in your list
Click the dropdown menu on the property detail modal
Select Run Calculator
The 5 inputs
The calculator walks you through five steps, each asking for inputs that drive the analysis.
Step 1: Purchase details
Purchase price. What you'll actually pay for the property
Down payment. Either a dollar amount or percentage. Standard rental loans require 20-25% down
Closing costs. Title fees, inspection, lender fees. A safe estimate is 2-5% of purchase price
Rehab budget. Any work needed before renting (paint, flooring, repairs)
Step 2: Loan terms
Interest rate. The rate on your mortgage
Loan term. Typically 30 years for rental property loans
Loan type. Conventional, DSCR, hard money, etc.
If you're paying cash, you can skip this section or set the loan amount to zero.
Step 3: Rental income
Monthly rent. What you expect to charge
Other income. Laundry, parking, pet rent, storage if applicable
Vacancy rate. A buffer for months the unit sits empty. 5-10% is common
Step 4: Operating expenses
Property taxes. Annual amount, typically pulled from the property data we already have
Insurance. Landlord policies usually run higher than owner-occupied
Property management. Usually 8-10% of monthly rent if you hire a manager
Maintenance and repairs. A reserve for ongoing fixes. 5-10% of rent is a common rule
Capital expenditures (CapEx). Long-term replacements like roof, HVAC, water heater. Another 5-10% of rent
HOA fees if applicable
Utilities if you're covering any
Step 5: Review
The final step shows you the calculated outputs based on everything you entered. You can go back and adjust any input to see how it changes the numbers.
What the outputs mean
The calculator returns four key metrics. Here's how to read each one.
Monthly cash flow
This is the cash that lands in your pocket each month after all expenses and the mortgage payment.
Monthly rent − all monthly expenses − mortgage payment = monthly cash flow
A positive number means the property pays you. A negative number means you're feeding the property each month. Most buy-and-hold investors look for at least $100-200/month per door in cash flow, though this varies by market.
Cash-on-cash return
This shows your return on the actual cash you put in (down payment, closing costs, rehab), expressed as an annual percentage.
(Annual cash flow ÷ total cash invested) × 100
A 6-8% cash-on-cash return is decent in many markets. 10%+ is strong. This metric tells you how hard your invested cash is working compared to other investments.
Cap rate (capitalization rate)
This shows the return the property would generate if you bought it in cash, ignoring financing.
(Annual net operating income ÷ purchase price) × 100
Cap rate is useful for comparing properties to each other and to market averages. A 5-7% cap rate is common for residential rentals in many markets. Higher cap rates often mean higher risk or worse locations.
Total return
This includes cash flow plus principal paydown on your loan plus any expected appreciation. It's the most complete view of what the deal earns you over time.
Tips for accurate analysis
Be conservative with rent. Use actual rent comps, not the highest number you see online
Don't skip vacancy and CapEx. Pretending these don't exist is the fastest way to underwater deals
Use real property tax numbers. Don't trust the seller's quote, pull from public records
Insurance is going up. Get a real quote, especially in coastal or wildfire areas
Run multiple scenarios. Try the deal with 5%, 10%, and 15% vacancy. If it only works at 5%, it's a fragile deal
Calculator limitations
The calculator is a planning tool. It does not: - Predict future rent growth or appreciation - Account for tax benefits (depreciation, deductions) - Replace the advice of a CPA or financial advisor - Calculate flip profits or BRRRR refinance scenarios (different math)
For complex scenarios like BRRRR, 1031 exchanges, or syndication deals, you'll want to do additional analysis outside the calculator.
Need more help? Email info@theinvestnest.com or use the chat bubble in the bottom-right of any page.