Structuring a Property Cash Flow Model That Someone Else Can Check

How to lay out a property investment model so assumptions are visible, calculations are traceable and a reviewer can challenge the judgement rather than the formulas.

A property model exists to expose the assumptions that carry a decision. If a reviewer has to trace formulas to find out what you assumed, the model has failed at its only job regardless of whether the arithmetic is correct. The structure below separates inputs, calculations and outputs so that judgement can be challenged directly, which is the only kind of review worth having.

Before stage one

Decide what the model is for before you open a spreadsheet. A model built to screen twenty assets is a different object from one built to support a committee decision on a single purchase, and trying to make one do both produces something that does neither well. Fix the question, the holding period and the audience first.

• A single stated purpose: screening, offer support, financing request or committee approval.
• The holding period and the periodicity, monthly or annual, decided and justified.
• A list of the decisions this model must inform, written before any cell is filled.
• The source documents in hand: leases, rent roll, invoices, survey and financing terms.
• Agreement on who owns the model and who is permitted to change assumptions.

Stage 1: Separate inputs, workings and outputs

Use three distinct areas, or three sheets. Inputs contain every number a human chose, each with a source note. Workings contain only formulas and no typed numbers. Outputs contain the summary a reader sees. The rule to enforce is simple: if a typed number appears in the workings area, it is an undeclared assumption, and undeclared assumptions are how models mislead the people who built them.

• Deliverable: A three-part structure with no hard-coded numbers outside the inputs area.
• Owner: Whoever builds the model.
• Approval gate: A search for typed constants in the calculation area returns nothing.

Stage 2: Build the assumptions page as a document

Each assumption needs a value, a unit, a source, a date and a named owner. Achievable rent cites the comparables schedule; the cost base cites the normalised statement; the exit yield cites the evidence it came from or admits that it is a judgement. This page is what a reviewer should spend their time on, so it should read like a short document rather than a column of figures.

• Deliverable: A one-page assumptions sheet with source, date and owner against every input.
• Owner: Model owner, with each contributor confirming their own lines.
• Approval gate: Every input has a named owner who has seen the value attributed to them.

Stage 3: Model the income from the rent roll upward

Drive income from a lease-level schedule rather than a single growth rate applied to a total. Each unit carries its own rent, expiry, review mechanism, incentive and assumed re-letting period. This is more work and it is the difference between a model that can answer questions and one that can only produce a number. It also means an expiry cluster is visible rather than hidden inside an average.

• Deliverable: A unit-level income schedule feeding the cash flow, with expiries and reviews on their dates.
• Owner: Analyst.
• Approval gate: Total income in the cash flow reconciles exactly to the sum of the unit schedule.

Stage 4: Model costs on their own drivers

Separate costs that are fixed, costs that vary with occupancy, costs that vary with collections such as a management fee, and costs that occur on events such as re-letting. Escalate each on an explicit assumption. Keeping these groups distinct is what allows a vacancy stress to behave correctly, because in a stress the fixed group must not fall.

• Deliverable: A cost schedule grouped by driver, each group with its own escalation assumption.
• Owner: Analyst.
• Approval gate: Running an occupancy stress leaves the fixed cost group unchanged.

Stage 5: Add the capital schedule and keep it outside net operating income

Bring in the dated capital expenditure schedule from the condition survey as its own block below net operating income. It affects cash, financing headroom and sometimes the exit value if works remain outstanding, but it must not touch the income measure. Keeping the boundary clean is what makes your net operating income comparable with the market evidence you are using.

• Deliverable: A capital block below net operating income with dated amounts and a funding source.
• Owner: Analyst with the surveyor's schedule.
• Approval gate: Net operating income contains no capital item and the capital block contains no operating cost.

Stage 6: Layer the financing beneath the asset

Model the asset unlevered first and complete it, then add debt as a separate layer with its own drawdown, repayment, fees and any cover tests. This ordering matters because it keeps the asset case and the financing case separable, so you can always report both. It also prevents the common error of using debt assumptions to rescue an asset that does not work.

• Deliverable: An unlevered cash flow and a levered one, both reported, with the debt layer self-contained.
• Owner: Analyst.
• Approval gate: Removing the debt layer leaves a complete and correct unlevered model.

Stage 7: Build the exit as an explicit block

Set the exit out with the forward year of income, the exit capitalisation rate, the gross value, selling costs, any outstanding debt to repay and the net proceeds. Show it as its own block rather than a single cell, because this is the number most likely to be challenged and it should be easy to examine. State clearly whether any transaction tax applies on disposal, which is a point to confirm with ZATCA for your circumstances.

• Deliverable: An exit block showing every component of the net proceeds on one screen.
• Owner: Analyst.
• Approval gate: The exit block can be read and challenged without opening any formula.

Stage 8: Finish with outputs, checks and a version record

The output page should carry net operating income, net yield, the unlevered and levered returns, the equity multiple, break-even occupancy, minimum cash balance and cover in the weakest year. Add check cells that confirm the balance reconciles, the income ties to the rent roll and no cost is double counted. Record the version, the date and what changed, because a model used in a negotiation will be revised many times.

• Deliverable: A one-page output sheet with working checks and a version log.
• Owner: Model owner.
• Approval gate: Every check cell reports clean before any version is circulated.

Handovers between stages

Models are usually built by one person and relied on by several, which is where errors become decisions. Hand over the assumptions page and the output page together, never the output alone, and require anyone proposing a change to state which assumption they are changing and on what evidence. Where the model supports a financing request or a valuation discussion, send the same version to everyone and record which version each party received.

How you know it is finished

The model is finished when a competent stranger can read the assumptions page, find every number's source, trace one income line and one cost line to the cash flow, and tell you which two assumptions carry the decision. Regulatory, tax and financing inputs change over time, so stamp the model with the date its assumptions were verified and re-verify before any decision taken months later.

Domira builds the numbers on a Saudi property with you before you commit: rent and cost evidence, condition and capital expenditure, the appraisal and the sensitivities that decide whether the deal survives a bad year. The investment decision stays yours, and so does the advice of your licensed tax and legal advisers.