## What this models
Purchasing a property from a chosen year: a scenario-only home is added, paid in cash or financed with
a mortgage, and optional recurring property tax, insurance, and HOA costs are added to the scenario's
expenses from the purchase year.
## Maps to module(s)
- `buy_house_v1` — set `purchase_price`, `down_payment`, and `purchase_calendar_year`. When financed
(down payment < price), set `rate_apr` and `term_years`. Optionally add `property_tax_annual`,
`home_insurance_annual`, `hoa_annual`, and one-time `transaction_costs`.
## Information needed
- Purchase price and down payment.
- Purchase year (within the planning horizon).
- If financing: mortgage rate (APR) and term in years.
## Defaults & assumptions
- **Default to all-cash**: if the user does not mention a mortgage, loan, down payment, or financing,
treat the purchase as all-cash (omit `down_payment` and `rate_apr`) — do NOT ask for an interest rate.
- Only model financing (set `rate_apr` and `term_years`) when the user says they will finance / take a
mortgage / put a partial down payment.
- Ask for the price and year if not given — don't guess the price.
## Prerequisites
- A completed baseline plan.
## How to summarize to the user
"Buy a {PRICE} home in {YEAR} with a {DOWN_PAYMENT} down payment{, financed at RATE% over TERM years}."
Educational content only—not personalized investment, tax, or legal advice.