You're under a tight LOI deadline and the sponsor expects an answer this week. Miss one lease detail and you might lose the deal. This guide is investor and broker acquisition underwriting — how you model cash flow, test debt, and decide whether to buy. It is not lender loan underwriting (what a bank does to approve your financing). For that side, read What Is Underwriting in Real Estate? Lender vs. Investor Explained.
Core idea — keep inputs clean, assumptions sharp, and outputs defensible
Acquisition underwriting is simple in theory: gather the facts, build the pro forma, test the debt, price risk. In practice it breaks down because inputs are messy, assumptions live in disconnected spreadsheets, and nobody documents why a price moved. Do three things: collect the right documents up front, force single-point assumptions into documented ranges, and stress-test the model for obvious failure modes. If you do that, your decisions will be repeatable — and the lender package you send later will match your conservative base case.
1) Data collection: what to pull first and why it matters
Start by pulling the documents that actually move cash: the rent roll, lease agreements, operating statements, tax bills, and any recent work orders or capital invoices. If you need to identify legal owners, follow our guide on How to Find Who Owns a Property: Commercial Owner Search. Industry practice recommends at least three years of operating statements when available. Don’t start modeling until you have those items.
On an investment deal in CREflow, attach those files to the property record and open the Underwriting tab — assumptions stay with the deal instead of a stray spreadsheet tab, so when a partner opens the file six weeks later the rent roll and model still match.
Key checks while collecting: For guidance on where diligence processes usually break and which tools help, see the best tools for managing due diligence.
- Match the rent roll to the leases. If a tenant is listed on the roll but there's no signed lease in the file, flag it and treat that cashflow as at-risk.
- Reconcile operating statements to tax returns if you can. Sellers and brokers sometimes present optimized statements; confirm the accounting basis.
- Get the true age and remaining life of major systems from work orders or engineer reports. Don’t assume capex is an item you can ignore.
Why this matters: sloppy inputs create false precision. You can paper over bad data with charts, but you can’t defend a price to partners or align a lender file if you missed a lease amendment.
2) Income normalization: make NOI defensible
Underwriting income isn't just copying the seller's numbers. You must show how you moved from Gross Potential Income (GPI) to Effective Gross Income (EGI) and then to Net Operating Income (NOI). Be explicit: list GPI, vacancy & collection loss, bad debt, non-reimbursable items, and other deductions.
In CREflow’s Underwriting tab, edit income and expense assumptions once — NOI, cap rate, cash-on-cash, IRR, and DSCR update live as you change inputs, so you see immediately when a vacancy tweak breaks your debt coverage.
Document every adjustment and why it’s reasonable. If you replace the seller’s vacancy number, tie your assumption to comparable market data or the rent roll's economic occupancy.
Common traps:
- Using historical recoveries without accounting for lease escalations or turnover.
- Assuming immediate market rents on turnover without vacancy and leasing costs.
- Counting reimbursements that are actually capital items.
Spell out your NOI bridge in the model so anyone can see the path from GPI to NOI without digging through tabs.
3) Expense analysis: fixed vs variable and capex reserves
Split expenses into fixed (taxes, insurance) and variable (utilities, repairs). Separate recurring maintenance from capital replacement. Build a capital reserve schedule — don’t hide future roof or HVAC costs in a generic "other" line.
Two practical habits that save deals:
- Run a unit-level expense sanity check. If maintenance per unit is an outlier versus local comps, ask why.
- Always add a capex reserve line and link it to building age or deferred maintenance items from the inspection report.
4) Debt analysis: make the loan math transparent
Debt is where underwriting either protects you or eats your equity. Lay out loan amount, interest rate, term, amortization, and then calculate Debt Service Coverage Ratio (DSCR). Use the standard DSCR formula: DSCR = NOI / Annual Debt Service. Include a conservative DSCR stress scenario in your underwriting — the same stress view you will later mirror for lender underwriting.
Run at least three debt scenarios: base, stressed, and recovery. Highlight the years where coverage is weakest — that’s where lenders and partners focus.
5) Value and return metrics: keep the formulas visible
Don’t hide the math. In your model keep these formulas visible and labeled so reviewers don’t have to guess how you arrived at price or returns:
- Cap Rate = NOI / Property Value
- Cash-on-Cash Return = Annual Pre-Tax Cash Flow / Total Cash Invested
- IRR: show projected cash flows and sale assumptions used to calculate IRR
If you adjust exit cap rates or terminal assumptions, document why. If you can’t cite a market data source for the exit cap, show sensitivity around that assumption.
Mini-case: a quick walkthrough
Picture a small retail strip under LOI with a mixed rent roll and an ambiguous lease for a long-standing tenant. You pull the rent roll and three years of P&L and find the tenant is paying below-market rent with an unrecorded amendment. You flag three actions:
- Confirm the lease amendment in writing and adjust GPI to reflect contracted rent.
- Build a vacancy and lease-up assumption tied to market leasing time for the submarket rather than assuming instant full occupancy.
- Add a targeted capex reserve for deferred roof work revealed in the inspection report and run a stressed DSCR scenario including that cash outlay.
Result: the pro forma shows weaker coverage in years one and two. You present the stressed model to the sponsor and either renegotiate price or require seller repair credits. That’s acquisition underwriting — it creates options; it doesn’t rubber-stamp optimism.
How to present underwriting so people can actually use it
Presentation is often underrated. Build a one-page investment memo with: deal summary, key assumptions, base and stress metrics (NOI, DSCR, exit cap), and the top three risks with mitigations. Attach the full model with color-coded tabs and a clear assumptions page. Avoid storing critical deal context in email — read about the true cost of storing deal notes in email.
When the memo is ready, use Share on CREflow’s Underwriting tab to send a read-only underwriting report to partners or investors — they see the same NOI, return metrics, and assumptions you used without editing your working model.
If you're still on spreadsheets, consider the guidance on when to switch from spreadsheets to deal management software. For teams that want assumptions, documents, and pipeline stage in one place, run acquisition underwriting on the CREflow Underwriting tab — linked to the deal and property so lifecycle history and attachments stay with the model.
Key takeaways
- This guide is investor/broker acquisition underwriting — distinct from lender loan underwriting.
- Collect clean inputs first: rent roll, leases, and at least three years of operating statements.
- Make NOI defensible: show every adjustment from GPI to NOI and link changes to market data or source files.
- Stress the debt: calculate DSCR using the NOI you derived and run clear stress scenarios.
- Keep formulas visible, share a read-only report from your underwriting tool, and document exit assumptions.
Also prioritize a healthy commercial real estate deal pipeline to keep vetted opportunities flowing.
FAQ
How is this different from lender underwriting?
Acquisition underwriting decides whether you should buy and at what price. Lender underwriting decides whether a bank will fund your loan. You need both, but start with your own model — see lender vs. investor underwriting explained.
How many years of statements should I ask for?
Ask for at least three years of operating statements when available. That gives you a sense of volatility and recurring items that might not appear on tax returns or the seller's summary.
What if the rent roll and leases don't match?
Flag it immediately. Treat unmatched items as a tenant-level and cashflow risk until you get documentation. Adjust GPI and EGI in your model and note the assumption as a conservative holdback until resolved.
Can CREflow replace my underwriting spreadsheet?
For acquisition deals, the Underwriting tab handles income and expense assumptions, live return metrics, and shareable reports tied to the deal. Complex one-off models may still use Excel — but assumptions and outputs should live with the deal record, not an orphaned file.
Should capex be in the NOI or separate?
Separate capex from recurring operating expenses. Capture routine maintenance in the expense section and list capital replacements in a reserve schedule. That keeps NOI comparable across deals.
Before You Underwrite — quick checklist
- Do you have the rent roll and signed leases? If not, stop and get them.
- Can you reconcile the seller’s operating statements to source documents? If not, add a conservative adjustment.
- Have you documented capex needs from inspections and linked a reserve in the model?
- Did you run a stressed DSCR scenario and note the weakest year?
- Can a partner reproduce the headline numbers from your one-page memo or shared underwriting report?
Ready to model your next acquisition in one place? Open CREflow and use the Underwriting tab on your investment deal — assumptions, metrics, and shareable reports stay linked to the property.
Try CREflow’s free commercial real estate underwriting calculator to model NOI, cap rate, DSCR, and IRR without a spreadsheet.