Source: https://guthlabs.ai/docs/instruments/rental-property-cash-flow-analyzer/

instrument / verified-with-binding-errata

# Rental Property Cash Flow Analyzer

The current ledger marks this instrument verified with errata that must be applied at binding time.

Status: **VERIFIED_WITH_ERRATA**Lifecycle: **verified-with-binding-errata**

## Inspectable records

[01**Overview**Purpose and lifecycle](<https://guthlabs.ai/docs/instruments/rental-property-cash-flow-analyzer/>)[02**Mechanism**Method and assumptions](<https://guthlabs.ai/docs/instruments/rental-property-cash-flow-analyzer/mechanism/>)[03**Implementation**Binding and validation](<https://guthlabs.ai/docs/instruments/rental-property-cash-flow-analyzer/implementation/>)[04**Qualification**Evidence and errata](<https://guthlabs.ai/docs/instruments/rental-property-cash-flow-analyzer/qualification/>)

## Ledger state

The current ledger marks this instrument verified with errata that must be applied at binding time.

**Area**: Finance, Economics & Business (educational only — never individualized investment, tax, or legal advice)

**Tranche**: tranche-5

**Evidence ID**: t5-166

**Ledger rows**: 1

No ledger note is attached.

## Review findings

The standard intended calculation under the stated assumptions is cash_flow = rent - mortgage_payment - taxes - insurance - HOA - rent*vacancy_pct - rent*maintenance_pct - rent*mgmt_fee_pct. The supplied formula is dimensionally invalid because currency amounts are mixed with percentage rates. Vector 2's expected result uses the corrected formula: 383 monthly and 4596 annual.

### Formula and scope findings

- The formula subtracts maintenance%, vacancy%, and property_mgmt% as raw numbers instead of converting them to expense amounts, such as rent*maintenance_pct.

- The formula does not define how annual net cash flow is calculated; it should be monthly_net_cash_flow*12 when all inputs are monthly.

- The formula does not define the expense-breakdown pie calculations.

- The claim "after all expenses" is incomplete because the listed formula omits potentially material expenses such as utilities, legal/accounting costs, licenses, repairs beyond the maintenance allowance, and capital expenditures.

### Unit assumptions

- Rent, mortgage payment, taxes, insurance, and HOA are assumed to be monthly amounts.

- Percentage inputs are assumed to be decimal fractions: 5% must be entered as 0.05, not 5.

- Maintenance, vacancy, and management percentages are assumed to apply to gross monthly rent.

- Annual cash flow is assumed to equal monthly cash flow multiplied by 12.

- Taxes and insurance must be converted to monthly amounts before calculation if supplied annually.

## Boundary hardening

**BREAK_CLAIMED** · SELF_FLAGGED

The extreme input overflows JavaScript arithmetic, and the zero-expense boundary makes expense-pie percentages undefined. The specification also lacks a stated branch or validation rule for percentages above 100% and does not clarify whether percentage inputs use percent points or decimal fractions.

## Errata and corrections

### Tranche errata

**monthly/annual_net_cash_flow** · vector 2

347 / 4164

383 / 4596

outputs contradict own working, which computes AND self-corrects to 383

## Inspectable example

4 review vectors are recorded. One source-bound sample is shown below.

````
{
  "inputs": {
    "rent": 2400,
    "mortgage_payment": 1200,
    "taxes": 200,
    "insurance": 100,
    "HOA": 50,
    "vacancy_pct": 0.05,
    "maintenance_pct": 0.08,
    "mgmt_fee_pct": 0.1
  },
  "expected_outputs": {
    "monthly_net_cash_flow": 298,
    "annual_net_cash_flow": 3576,
    "expense_breakdown": {
      "mortgage": 1200,
      "taxes": 200,
      "insurance": 100,
      "HOA": 50,
      "vacancy": 120,
      "maintenance": 192,
      "property_management": 240,
      "total_expenses": 2102
    }
  },
  "working": "Vacancy = 2400*0.05 = 120. Maintenance = 2400*0.08 = 192. Management = 2400*0.10 = 240. Total expenses = 1200+200+100+50+120+192+240 = 2102. Monthly cash flow = 2400-2102 = 298. Annual cash flow = 298*12 = 3576."
}
````

## Related workflows

No source-defined multi-instrument workflow membership is recorded.

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json · VERIFIED_WITH_ERRATA`

- `evidence-tranche5/tranche5-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`