Build a Financial Model an Investor Will Believe

    You are a startup CFO. Help me build a financial model that is a reasoning tool first and a fundraising document second.

Business model: {{how_you_make_money}}
Current numbers: {{revenue_customers_costs}}
Sales motion: {{self_serve_sales_led_or_mixed}}
Unit economics if known: {{cac_ltv_margin}}
Horizon: {{how_many_years}}

The test for the whole model: every number should trace to an assumption you can argue about. A model whose revenue line grows because the previous cell times 1.2 is not a model, it is a wish with a spreadsheet around it. Investors do not read the forecast to learn the future; they read it to learn how you think.

Part 1 — Build revenue from drivers, not from a growth rate. Depending on my motion, that means:
- Sales-led: leads → qualified → won, with conversion rates and a real sales cycle length; reps hired, ramp time before productivity, and quota attainment that is not 100%
- Self-serve: traffic → signup → activation → paid, with retention applied by cohort
- Either way: layer cohorts so churn compounds correctly. Applying a flat monthly churn to a total revenue number understates the damage every time.

Part 2 — Costs, bottom-up:
- Every hire as a line with a start month and a fully loaded cost
- Variable costs that scale with revenue, kept separate from fixed
- Marketing as a function of the acquisition you modelled, not as a percentage of revenue you hope to have
- The things founders forget: payroll taxes and benefits, software per seat, professional fees, the office, bad debt, payment processing

Part 3 — Test it before anyone else does:
- Does the implied CAC payback and LTV-to-CAC ratio make sense, and do they improve or deteriorate over time? Deteriorating unit economics inside a hockey stick is the first thing a good investor checks.
- Does revenue per employee reach a plausible level, or does the model imply an efficiency no company in this category has achieved?
- Does the sales team in year three have to close a number of deals that a team that size has never closed?
- What does the model imply about the market size you claimed? If year five revenue is a large fraction of your SAM, one of the two is wrong.

Part 4 — Make the assumptions visible. Every input on one tab, labelled, with the source and my confidence in each. Then run three cases — base, downside where the two most sensitive drivers miss, and upside — and tell me which single assumption moves the outcome most. That variable is what your business actually depends on, and knowing it is the point of the exercise.

Flag any assumption where I have given you nothing and you would otherwise have invented a plausible number.