Underwriting methodology
How DealPrism sources and verifies property data
Not every input has the same confidence. DealPrism preserves source and status context, lets you replace important assumptions, and sends resolved values through deterministic financial calculations.
Source categories
- RentCast supplies property records, valuation estimates, rental estimates, and ZIP-level market inputs where those endpoints return data.
- Google Maps / Places supports address search and structured location details. It is not the source of underwriting math.
- Brave Search discovers recent sources for market-intelligence context. Retrieved claims remain linked to their evidence.
- OpenAI summarizes retrieved market evidence and explains computed deal outputs. It does not produce authoritative underwriting calculations.
- User-provided values are explicit deal inputs or overrides and remain visibly labeled.
- DealPrism defaults fill gaps with clearly labeled assumptions that users can replace.
Field-level source guide
| Field | Possible source | Status label | How used | What you should verify |
|---|---|---|---|---|
| Purchase price | Active listing when available, otherwise user input | Listing data or User provided | Acquisition basis for the analysis | Current asking price and negotiated terms |
| Estimated market value | RentCast AVM or supported provider signal | Estimated | Equity, value, and refinance context | Recent comparable sales and property condition |
| Monthly rent | RentCast estimate, supported listing signal, or user input | Estimated, Listing data, or User provided | Rental income used by the engine | Local rent comps and lease terms |
| Taxes | Provider property record or user input | Public record / provider record or User provided | Annual operating expense | Current tax bill and reassessment risk |
| Insurance | User input or DealPrism default | User provided or Default | Annual operating expense | Property-specific carrier quote |
| Interest rate | Profile preference, user input, or DealPrism default | User provided or Default | Debt-service calculation | Current lender quote and loan fees |
| Vacancy | Profile preference, user input, or DealPrism default | User provided or Default | Reduces effective rental income | Local vacancy and turnover history |
| Maintenance | User input or DealPrism default | User provided or Default | Operating reserve | Age, condition, and actual service history |
| CapEx | User input or DealPrism default | User provided or Default | Long-term capital reserve | Roof, HVAC, plumbing, and major replacements |
| Management | Profile preference, user input, or DealPrism default | User provided or Default | Operating expense | Local manager proposal or self-management plan |
| Unit count | User input, explicit provider field, property-type inference, or listing-text inference | User provided, Provider record, or Derived | Per-unit facts and expense scaling | Legal unit count and current occupancy |
| Rehab | User input or clearly labeled estimate | User provided or Estimated | Upfront cash and BRRRR analysis | Contractor scope and contingency |
| ARV | User input or supported valuation estimate | User provided or Estimated | BRRRR/refinance scenario context | Renovated comparable sales and appraisal |
How values are resolved
Resolution is field-specific rather than one universal fallback chain. An explicit current-deal edit takes precedence when the analysis is recalculated. Profile preferences can seed financing and operating assumptions. Property values may use an active listing before an AVM, while unit count follows user input, explicit provider data, deterministic property-type inference, supported listing-text inference, then an unknown state.
DealPrism keeps the selected value and its source metadata together so an estimate cannot silently appear as a verified fact.
The deterministic calculation boundary
DealPrism's financial metrics are calculated by deterministic backend code. The AI layer explains and discusses those computed results but does not produce the authoritative cash flow, cap rate, cash-on-cash return, or DSCR values.
Freshness and timestamps
Provider responses may include an “as of” timestamp. RentCast snapshots are cached for a configured maximum age, and market-context retrieval favors recent sources. When freshness is unavailable or a source is stale or conflicting, DealPrism preserves that uncertainty through source metadata and verification flags instead of treating the value as current fact.
What to verify before relying on an analysis
- Rent comps and current lease terms
- Property taxes and reassessment exposure
- Landlord insurance quotes
- Lender rate, fees, amortization, and down payment
- Rehab scope, bids, and contingency
- Owner-paid utilities and other operating expenses
- Legal unit count, occupancy, and property condition
Review the assumptions on a real deal
Create a free Explorer account to run an analysis, inspect source labels, and replace estimates with property-specific information.
Results are based on user-entered assumptions. Values may vary by property, location, and market conditions. Review all assumptions before making investment decisions.