Category
Conversion headroom, withdrawal sequencing, and account-level tradeoffs.
Liquidity
Solo 401(k) Loan vs HELOC Calculator
Compare payments, interest, and opportunity cost when funding a down payment with a Solo 401(k) loan versus a HELOC (using your inputs).
On This Page
2 planning notes, 3 FAQs, and source links for follow-up.
Workflow
Start with sample inputs, review the live output, then save the assumptions you plan to act on.
Why This Tool Exists
People argue about which is cheaper. The real question is which is less fragile when reality happens: timeline slips, rates change, or cash flow tightens.
This calculator helps you compare the cash flow and the hidden cost (opportunity cost) so you can pick the tool that matches your risk tolerance.
Execution note: Run the tool, then write down your assumptions and keep the receipts and logs as you go. The strategy that wins on paper only matters if your process holds up in the real world.
Loan Comparator (HELOC vs 401k Loan)
Compare payment, interest cost, and opportunity cost using conservative assumptions.
HELOC payment (est.)
$0
401(k) loan payment (est.)
$0
Opportunity cost (est.)
$0
| Scenario | HELOC rate | HELOC interest | Opp. cost | Quick read |
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This is a planning model. Taxes, deductibility, and plan rules can matter. The win is choosing the option that stays stable when the timeline slips.
What To Model (So You Do Not Fool Yourself)
The payment you can actually afford matters more than the interest rate you prefer.
Opportunity cost is the hidden lever on retirement-account loans. If markets go up while your money is out, that is a cost.
For HELOCs, rate risk is the hidden lever. Model a higher rate scenario to stress test.
Execution Notes
Pick a conservative expected return for opportunity cost. Optimism is how you rationalize bad leverage.
If you are using leverage for a down payment, pair it with a written downside plan and liquidity reserves.
Keep your documentation clean. Lenders and advisors care about the paper trail.
Documentation Checklist (Keep It Defensible)
- Create a one-page objective memo before you execute (what outcome you are trying to buy).
- Store your assumptions and calculations in a dated PDF (no year-end reconstructions).
- Keep evidence in the same folder structure every month (receipts, logs, approvals).
- Ask your CPA what would make this easy to sign off on, then build that packet.
Primary Sources To Verify Before You Act
Use primary guidance and your own records before you treat any page like a final answer. These are the source layers that should drive the decision.
- IRS retirement plan guidance and IRA rules
- Medicare premium and IRMAA guidance
- Current IRS forms, instructions, and publications for the relevant tax year
- Your actual account statements, payroll reports, entity records, and advisor memos
Frequently Asked Questions
The interest is paid back into the account, but the opportunity cost (missed market returns) can be real. This tool models both.
It depends on facts and use. This tool is a cash flow model. Ask your CPA for deductibility rules in your situation.
Safety depends on rate volatility, repayment flexibility, and your liquidity buffer. Use the stress inputs to see how fragile each option is for you.
Use The Tool, Then Build The Full Plan Live
Before You File runs live on Zoom from Friday, April 17, 2026 through Sunday, April 19, 2026, from 10 AM to 4 PM Eastern each day. Preston walks through how to read your 2025 return, choose the right tax and wealth moves, and leave with a dated 12-month 2026 plan.
Get Your Seat Before You FileEducational content only. Results vary based on your facts. Always consult a qualified tax professional before making decisions.