Use one formula
Three-year cost = subscription + usage fees + implementation + migration + integrations + internal labor.
Ask for the fee schedule
Request prices for ACH, cards, screening, eSignatures, SMS, extra users, API access, onboarding, data imports, and cancellation exports. Separate fees paid by tenants from fees absorbed by the business.
Price growth before it happens
Calculate the cost at the current unit count, the expected count in 18 months, and a stalled-growth case. This exposes per-unit increases and flat-tier cliffs.
Use the full flat-rate vs per-unit cost method.