You borrow fiat, buy BTC immediately at today's price, then evaluate the outcome at your chosen exit date. Net profit = BTC value at target price − total payments made − remaining loan balance. Break-even price is the BTC price where net profit equals zero.

Amortizing — Fixed monthly payments of principal + interest. Standard for mortgages, HELOCs, personal loans, and 401k loans. Uses the standard amortization formula: M = P × r(1+r)ⁿ / ((1+r)ⁿ−1).

Interest-Only — Monthly payments cover interest only. Full principal is due at maturity. Payment = Principal × APR / 12. Common for bridge loans and some HELOCs.

Accruing (No Payments) — Zero monthly payments. Interest compounds monthly on the full balance: Balance = P × (1 + r)ⁿ. Used for margin loans, BTC-backed lending, and hard money loans. For BTC-backed loans, you pledge existing BTC as collateral at a given LTV ratio. Liquidation price = BTC price today × LTV%. For example, at 50% LTV and $100k BTC, liquidation occurs at $50k (a 50% drop). Margin loans use your brokerage portfolio as collateral, so BTC-specific liquidation does not apply.

Balloon — Monthly payments based on a 30-year amortization schedule applied to the full principal, with the remaining balance due as a lump sum at the end of the actual term. Interest accrues on the full outstanding balance each month.

The DCA alternative models investing the same monthly payment amount into BTC over the exit period. For accruing loans (no payments), it uses the loan amount divided by the number of months as the monthly investment. BTC price is assumed to grow linearly from today's price to 50% of the way toward the target price, simulating a gradual uptrend rather than a sudden jump. This is a simplification — real price paths are volatile and non-linear.

BTC target price buttons use a power law regression model: log₁₀(price) = a + b × log₁₀(days since genesis). Genesis date: January 3, 2009. Floor applies a 0.42× multiplier, Fair uses the regression line, and Ceiling applies a 3× multiplier. These update automatically when you change the exit timeline.

Tax implications (interest deductibility, capital gains on BTC sale), variable or adjustable interest rates, early repayment penalties, margin call mechanics beyond simple liquidation price, 401k job separation risk (full balance due if you leave your employer), daily interest compounding (model assumes monthly), and BTC transaction fees or exchange spreads.

The price × time heatmap shows net profit across a range of BTC exit prices and exit timelines, holding all other inputs constant. Green cells are profitable, red cells are losses, with intensity reflecting magnitude.