The 5 Numbers Every Real Estate Investor Must Know Before They Buy

Every bad real estate investment has one thing in common: the investor did not know their numbers before they bought. These are the five numbers that matter most — the ones professional investors calculate before they make a single offer.

Number 1 — Net Operating Income (NOI)

NOI is the foundation of every real estate analysis. Formula: Gross Rental Income - Operating Expenses = NOI. Operating expenses include property taxes, insurance, management fees, maintenance, and vacancy allowance — but NOT mortgage payments.

Why it matters: NOI determines a property's value in the commercial world (Value = NOI ÷ Cap Rate), its ability to service debt (DSCR = NOI ÷ Debt Service), and its attractiveness to future buyers. A property with strong NOI growth is a compounding wealth machine. A property with shrinking NOI is a liability.

Number 2 — Cash Flow

Cash flow = NOI - Mortgage Payments. This is the number that determines whether you receive a check or write one every month. Positive cash flow properties pay you to own them. Negative cash flow properties cost you money every month.

The threshold question: how much negative cash flow can you absorb, and for how long, before it becomes a problem? Some investors accept modest negative cash flow in high-appreciation markets. Most investors, especially newer ones, should require at least breakeven cash flow before acquiring a property.

Number 3 — Cash-on-Cash Return

Formula: Annual Cash Flow ÷ Total Cash Invested. This tells you the return on your actual out-of-pocket investment — the down payment, closing costs, and initial repairs.

A property requiring $80,000 in total upfront investment that generates $8,000/year in cash flow has a 10% cash-on-cash return. In today's rate environment, 6-10% is a strong result for a leveraged rental property.

Number 4 — DSCR

Debt Service Coverage Ratio = Annual NOI ÷ Annual Debt Service. This is the number your lender cares about most, and you should too. A DSCR below 1.0 means the property cannot cover its own mortgage from rental income — a fundamental problem.

Target 1.25x or higher. This gives you a 25% cushion against vacancy, unexpected repairs, or rent reductions before the property starts costing you money.

Number 5 — Maximum Allowable Offer (MAO)

MAO is the most important number for deal acquisition. It is the highest price you can pay and still hit your return targets. Starting from your target cash-on-cash return, work backwards to determine the maximum price that makes the deal work.

Most investors use a simplified version: MAO = (Monthly Rent × 100) - Rehab Costs - Required Profit. A property renting for $1,500/mo with $20,000 in needed repairs has a MAO of approximately $130,000 (150,000 - 20,000) at the 1% rule. Adjust based on your market and return requirements.