The SBLOC scenario now shows collateral call risk — how far your portfolio can fall before a margin call, and what curing one would cost. Read the write-up.
Keep your portfolio invested while buying a home
See the real cost of all three options. Tax implications included.
Stockstead calculator
Models three financing paths for a high-net-worth home purchase: paying cash, a traditional jumbo mortgage, and a Securities-Backed Line of Credit (SBLOC). Accounts for federal long-term capital gains, the 3.8% Net Investment Income Tax, state capital gains tax, the mortgage interest deduction up to the $750K acquisition-debt cap, opportunity cost of any liquidated investments, and SBLOC interest carry over your chosen horizon.
The interactive calculator requires JavaScript. With JS enabled you can change home price, portfolio value, cost basis, tax bracket, state, expected returns, and lender rates — and see the after-tax cost of each path side-by-side.
Worked example — $1.5M home, $2M portfolio, 10 years
A buyer with $150,000 in cash and $2,000,000 in taxable stock at a 50% cost basis needs a $300,000 down payment. Cash covers half, so the rest comes from selling stock or from an SBLOC — or the SBLOC covers all of it and the cash stays invested. Every path takes a 7.39% jumbo mortgage for the rest. Assumes a 7.27% SBLOC, 28.5% combined capital-gains rate, 7% expected portfolio return, and rates as of October 8, 2026. Computed by the calculator above.
| Down payment funded by | Cap-gains tax at purchase | Interest paid, 10 years | Portfolio after 10 years | Net position after 10 years |
|---|---|---|---|---|
| Sell stock for the gap | $24,927 | $835,045 | $6,540,922 | $7,517,796 |
| SBLOC for the gap | $0 | $944,095 | $6,885,030 | $7,556,460 |
| SBLOC for the full down payment | $0 | $1,053,145 | $7,180,102 | $7,546,090 |
Borrowing the gap finishes +$38,665 versus selling stock: it avoids the capital-gains tax and keeps the stock compounding, but pays $109,050 more interest. The edge is thin and depends on the portfolio out-earning the SBLOC rate — at a 6% return, borrowing the full down payment finishes −$13,401. An SBLOC also carries margin-call risk that selling stock does not.
Your numbers will differ — tax bracket, cost basis, expected return, and rate spread all change the answer. Use the calculator above to model your situation, or read the full SBLOC vs mortgage vs cash pillar guide for the full derivation, citations, and edge cases.
Three ways to fund a home purchase from an investment portfolio
If you're buying a home and you have a large taxable investment portfolio, your three options are not equal. Each has a different tax consequence, a different opportunity cost, and a different risk profile. Stockstead compares them side-by-side with the math your mortgage calculator is missing.
Pay cash
Liquidate enough of your portfolio to cover the full purchase. Simple, but you realize capital gains — up to federal 20% + 3.8% NIIT + state — and you lose future compounding on the money you pulled out. For a long-held, appreciated portfolio, this is usually the most expensive option. See the worked example on why this often costs more than it appears.
Traditional mortgage
Put 10–20% down and finance the rest. Your portfolio mostly stays invested, and mortgage interest on the first $750K of principal is tax-deductible on a primary residence. You still realize some capital gains on the down payment, though, and rates matter — at 6%+ mortgage rates, interest compounds fast over 30 years.
SBLOC (Securities-Backed Line of Credit)
Borrow against your portfolio rather than selling it. No capital gains event; your portfolio stays invested and compounding. The trade-offs: higher variable rates (typically prime + 1–2%), margin-call risk if markets fall, and interest is generally not deductible the way mortgage interest is. For the mechanics — advance rates, maintenance ratios, and how margin calls actually trigger — see our complete guide to how an SBLOC works. For the strategic decision framework on buying a home without selling investments, read the deep-dive. The full three-way comparison with a $1.5M worked example is in our pillar guide.
What the calculator does
You enter your purchase price, down payment, portfolio value, cost basis, tax bracket, expected returns, and time horizon. Stockstead computes the after-tax cost of each option — including federal + state capital gains, the 3.8% Net Investment Income Tax, opportunity cost, and SBLOC interest — so you can see which strategy actually wins for your situation. No signup. No data leaves your browser.
Weighing borrowing against your portfolio versus tapping home equity? The dedicated SBLOC vs HELOC after-tax calculator runs that specific comparison — effective after-tax rate on each path, accounting for the deductibility difference and any capital-gains drag.
This is an educational tool, not personalized financial advice. Always confirm a strategy with your tax and wealth advisors before acting.
Common questions
- What is an SBLOC and why compare it to a mortgage?
- A Securities-Backed Line of Credit (SBLOC) lets you borrow against your investment portfolio without selling it. Compared to a mortgage, it avoids triggering capital gains taxes and keeps your portfolio invested — but the rate floats with SOFR, can be higher or lower than a mortgage depending on the lender, and there is margin-call risk if markets fall.
- Who is this calculator for?
- High-net-worth home buyers with a meaningful taxable investment portfolio — people for whom liquidating $100K+ in stock to fund a down payment would trigger material capital gains taxes or opportunity cost.
- Does it account for capital gains tax and opportunity cost?
- Yes. The calculator models federal long-term capital gains, state capital gains, the 3.8% Net Investment Income Tax, expected portfolio return, and the compounded opportunity cost of any money pulled out of the portfolio.
- Is anything saved to a server?
- Not your numbers. Calculations run in your browser, and your exact inputs are never sent to Stockstead unless you create an account to save a scenario. Anonymous usage analytics record only coarse ranges (for example, a home price of $1M–$1.5M). See the privacy policy for details.
More answers on the FAQ and in the full answers index.
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