A pro forma (Latin for 'as a matter of form') is a projected income statement for a property, not a report of what happened but a best-guess picture of what will happen. Investors and lenders use it to stress-test a deal before money changes hands. A well-built pro forma starts with Gross Potential Rent (GPR), the total rent collected if every unit is occupied and paying on time 365 days a year. From GPR, you subtract a vacancy and credit-loss allowance (typically 5 to 10 percent of GPR for stabilized assets) to arrive at Effective Gross Income (EGI). Then you layer in any other income sources, parking fees, pet fees, laundry revenue, and the like, to get your true top-line number.
Operating expenses come next. These include property taxes, insurance, property management fees (commonly 8 to 12 percent of collected rent), repairs and maintenance, utilities the landlord pays, landscaping, and a capital expenditure reserve for big-ticket replacements like roofs, HVAC systems, and appliances. Subtract total operating expenses from EGI and you get Net Operating Income (NOI): the single most important number in any pro forma. The formula is: NOI = EGI - Operating Expenses. NOI is used to calculate cap rate (Cap Rate = NOI / Purchase Price) and to size debt through the Debt Service Coverage Ratio (DSCR = NOI / Annual Debt Service). Lenders typically require a DSCR of 1.20 or higher, meaning NOI must cover mortgage payments by at least 20 percent. After debt service, what remains is your pre-tax cash flow, which feeds the Cash-on-Cash Return calculation: Cash-on-Cash = Annual Pre-Tax Cash Flow / Total Cash Invested.
The biggest risk with any pro forma is optimism bias. Sellers and their brokers routinely present proformas that assume 100 percent occupancy, below-market expense ratios, and rent bumps that require immediate lease-up at top-of-market rates. Always rebuild the proforma from scratch using current market rents from comparable listings, actual tax bills, real insurance quotes, and a management fee even if you plan to self-manage (because circumstances change). A conservative proforma uses a 10 percent vacancy rate, a fully-loaded expense ratio of 35 to 50 percent of EGI for most residential assets, and a CapEx reserve of at least 5 to 10 percent of gross rents. If the deal pencils at those inputs, the margin of safety is real.
Worked example
A duplex lists for $400,000. Each unit rents for $1,500 per month, so Gross Potential Rent is $36,000 per year. Apply a 7 percent vacancy allowance ($2,520), giving EGI of $33,480. Add $1,200 in annual laundry income for a total EGI of $34,680. Operating expenses break down as follows: property taxes $4,200, insurance $1,800, management fee at 10 percent of collected rent $3,348, repairs and maintenance $2,400, and a CapEx reserve of $1,800. Total operating expenses equal $13,548. NOI = $34,680 - $13,548 = $21,132. Cap Rate = $21,132 / $400,000 = 5.28 percent. The buyer puts 25 percent down ($100,000) and finances $300,000 at 7 percent for 30 years, producing annual debt service of roughly $23,959. Pre-tax cash flow = $21,132 - $23,959 = -$2,827, a slight negative. DSCR = $21,132 / $23,959 = 0.88, which most lenders will reject. This proforma tells the investor the deal only works at a lower price, with a lower interest rate, or with value-add rent growth baked in with realistic assumptions.