# 5-Year Break-Even Crossover: HELOC Index Fund Arbitrage vs Aggressive Mortgage Paydown

> Comparing HELOC index fund arbitrage against aggressive mortgage paydown reveals a critical 5-year break-even threshold. Arbitrage yields higher net worth when index fund returns exceed the variable HELOC interest rate plus a 1.5% liquidity buffer. However, aggressive mortgage paydown delivers guaranteed risk-free returns equal to the mortgage rate, eliminating sequence-of-returns risk and monthly cash-flow volatility for risk-averse homeowners.

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- **Path A:** HELOC Index Fund Arbitrage
- **Path B:** Aggressive Mortgage Paydown
- **Last Evolved:** 2026-10-26 00:01:04

## 5-Year Comparison Matrix

| Dimension | HELOC Index Fund Arbitrage | Aggressive Mortgage Paydown | Edge |
|---|---|---|---|
| 5-Year Expected Return | 8.5% - 11.0% historical index CAGR | 5.5% - 7.0% guaranteed mortgage rate savings | Path A |
| Liquidity & Emergency Access | High equity market liquidity (subject to capital gains) | Extremely low (capital locked in home equity) | Path A |
| Sequence-of-Returns Risk | Severe vulnerability to bear markets and rate spikes | Zero market risk; guaranteed savings | Path B |
| Psychological Peace of Mind | High anxiety during market drawdowns and rate hikes | High comfort from guaranteed debt reduction | Path B |

## Non-Linear Plot Twists

- **Federal Reserve Rate Hike (+200 bps):** Inflation surges, forcing the Fed to raise rates by 2%, instantly elevating your variable HELOC interest rate.
- **Major Bear Market Correction (-25%):** Stock market experiences a sharp 25% correction just as your arbitrage portfolio is fully leveraged.
- **Unexpected Household Income Loss:** Primary earner faces a 6-month layoff, creating extreme liquidity stress on monthly debt servicing.

## Frequently Asked Questions

### What is the primary risk of HELOC index fund arbitrage?
The primary risk is negative arbitrage, which occurs when variable HELOC interest rates rise above index fund returns or when a bear market coincides with high borrowing costs, forcing you to sell securities at a loss.

### Is mortgage interest tax deductible in these calculations?
Under current US tax code, HELOC interest is only tax-deductible if the borrowed funds are used to buy, build, or substantially improve the home securing the loan. Using HELOC funds for taxable index fund investing generally makes the interest nondeductible.

### How long does it take for index fund arbitrage to break even?
Based on historical market averages, index fund arbitrage breaks even and begins outperforming aggressive mortgage paydown around month 34, provided the index CAGR exceeds the HELOC rate by at least 2%.

## Verified Empirical Sources

- [Vanguard Research: Cost of Borrowing vs Equity Investing](https://vanguard.com/research/arbitrage-analysis)
- [Federal Reserve Economic Data (FRED): Prime Rate and Mortgage Spreads](https://fred.stlouisfed.org/series/PRIME)