Rental Property Deal Analyzer in Google Sheets: Evaluate Any Investment Before You Buy (2026)

Buying a rental property on gut feel is how investors lose money. A deal analyzer in Google Sheets runs the real numbers — cash flow, cap rate, cash-on-cash return, and NOI — in minutes, before you make an offer you'll regret.

Why You Need a Deal Analyzer — Not a Gut Check

Every rental property investor has a story about the deal that "felt right." Most of those stories end with a property that barely breaks even — or worse, loses money every month while the owner prays for appreciation.

The problem is that real estate sales are designed to look attractive. A listing showing $2,400/month rent on a $280,000 property sounds great. But run the actual numbers — mortgage, taxes, insurance, vacancy, repairs, CapEx reserves, and management fees — and that "cash flowing" property might be losing $200 a month.

A deal analyzer forces honesty. It takes every input, applies realistic assumptions, and gives you three numbers that don't lie: cash flow, cap rate, and cash-on-cash return. If a deal doesn't pass all three, it doesn't pass.

The 5 Numbers Every Deal Must Pass

Before building anything, understand the five metrics your analyzer needs to calculate. These are the standard measures professional real estate investors use to evaluate deals.

1. Gross Rental Income (GRI)

The total rent you could collect if every unit was rented 100% of the time. This is your theoretical maximum — you'll discount it for vacancy next.

2. Net Operating Income (NOI)

The income left after vacancy losses and all operating expenses — but before mortgage payments. This is the most important metric for evaluating a property's performance independent of how you finance it.

3. Cap Rate (Capitalization Rate)

Cap rate tells you the yield you'd get if you bought the property with all cash. It's the universal language of commercial real estate — it lets you compare properties regardless of financing.

Target: In most markets, look for cap rates of 5–8%. Below 4% is speculation territory (betting on appreciation). Above 10% usually signals higher risk (rough area, deferred maintenance, low-quality tenants).

4. Cash Flow

What actually hits your bank account each month after everything — including debt service. This is what most new investors focus on, and it's what keeps you solvent.

Target: $200+ per door per month minimum for a deal worth owning. Less than that and you have no buffer for surprises.

5. Cash-on-Cash Return (CoC)

CoC measures the return on the actual cash you invested — your down payment plus closing costs plus any rehab. This is the number that competes with your other investment options (stock market, bonds, etc.).

Target: 8–12% CoC is excellent. Below 6% and you're better off in index funds with no landlord headaches. Above 15% — double-check your assumptions, something is probably too optimistic.

How to Structure Your Deal Analyzer

Your Google Sheets deal analyzer should have four tabs. Keep each tab focused on one job so the whole spreadsheet stays readable and easy to update as you refine the deal.

Tab 1: Deal Inputs

This tab is the control center. Every other tab references these cells using named ranges or cell references. Change one number here and everything updates automatically.

In Google Sheets, create this table starting in row 2. Give column A the label, column B the input value, and column C a brief note.

Purchase Details

Financing Details

Property Details

Tab 2: Income Projections

This tab calculates what you'll actually collect, accounting for vacancy. Optimistic investors use 0% vacancy. Experienced investors use 5–10% depending on market conditions and property class.

Using the example inputs above: $1,800 × 2 units × 12 months = $43,200 GRI. At 7% vacancy, that's $3,024 in lost rent, leaving you with $40,176 in effective gross income.

Tab 3: Operating Expenses

This is where most amateur deal analyzers go wrong. They forget half the expenses. Here are every cost you need to include — and reasonable benchmarks for each.

Fixed Annual Expenses

Variable/Reserve Expenses

The 50% Rule: A Quick Sanity Check

Before running full numbers, experienced investors use the 50% Rule as a quick filter: operating expenses on a rental property (excluding mortgage) typically run 40–50% of gross rent. If a property's expenses exceed 50% of gross rent before the mortgage, it's a tough deal.

Tab 4: Returns Dashboard

This is where everything comes together. Pull all figures from the previous tabs to calculate your five key metrics in one clean dashboard.

Example Deal: The Numbers on Our $280K Duplex

Running Scenarios: Best / Base / Worst Case

Never buy a deal that only works in the best case. Add a scenario section to your Returns dashboard that tests three versions of reality.

If your deal is cash flow negative in the worst case and you can't absorb the loss, it's too risky. The test: can you survive 3 months of vacancy plus a $5,000 repair bill in the same year? If the numbers say yes, the deal is stress-tested.

In Google Sheets, use Data Validation dropdown on a "Scenario" cell with options Best/Base/Worst, then use IF() or IFS() formulas to switch inputs automatically. This makes the analyzer interactive with one click.

Deal Benchmarks by Market Type

What "good numbers" look like depends heavily on your market. Adjust expectations accordingly:

In high-cost markets, investors tolerate lower cash flow because they're betting on appreciation. In cash flow markets, appreciation may be flat but the monthly income is strong. Neither strategy is wrong — you need to know which you're playing.

Red Flags That Kill a Deal

Your deal analyzer will flag these automatically if you build it correctly. Watch for:

• Negative cash flow at base case vacancy: A 5–7% vacancy assumption turning cash flow negative means you have no margin for a bad year.
• CoC below 5%: You can earn that in a high-yield savings account with zero landlord headaches.
• Cap rate below 4%: You're paying for appreciation, not income. That's speculation.
• Rent-to-price ratio below 0.5%: The "1% rule" (monthly rent ≥ 1% of purchase price) is outdated in many markets, but below 0.5% means the deal fundamentally doesn't cash flow.
• Expenses based on seller's numbers: Sellers understate expenses. Always use your own benchmarks, not theirs.
• No CapEx reserve: If your analyzer shows great cash flow but you forgot to include roof/HVAC reserves, the real cash flow is lower.

Skip the Build: Get a Ready-Made Rental Property Template

Building a deal analyzer from scratch takes 3–5 hours if you want to do it properly — with named ranges, scenario switching, error handling, and a clean layout that doesn't break when you hand it to a partner or spouse.

If you'd rather have something that works immediately, the SheetStackStudio rental property templates are built for exactly this workflow: input your deal details, get clean metrics instantly, and move on to the next deal.

The Bottom Line

A rental property deal analyzer doesn't make decisions for you — it gives you the information to make good ones. Every input you change tells you something: what price makes this deal work, how sensitive it is to vacancy, whether a price reduction changes the math.

The investors who lose money are the ones who do the math in their head and round up on optimism. The ones who build wealth do the math in a spreadsheet and negotiate from facts.

Build your analyzer once. Run every deal through it. The 3 hours you spend building it will save you from one bad deal that would cost 30x more.