How Much a Second-Lien HELOC Costs Next to a Low First Mortgage

The Quick Read: A second-lien HELOC on a rental costs the interest on the new line applied only to the new balance, plus fees, while the low first mortgage keeps its own terms, so the true cost is a balance-weighted blend of both loans rather than the line’s pricing alone. Through select lenders in Lendmire’s wholesale network, an investment-property line is capped at 70% combined loan-to-value and $500,000, subject to lender guidelines.

• The first mortgage is not paid off, repriced, or reissued. Its balance, term, and payment stay as written.
• Combined loan-to-value (CLTV) sets the size of the line, and a small line makes fixed fees weigh more.
• Investment lines in the network float through both the draw and repayment periods and never convert to fixed.
• The line is underwritten on the borrower, not on the rent, so it answers a different question than a DSCR loan.

What Does the Line Actually Cost Beside the First Loan?

The cost is a weighted average, not one number. The new line carries a higher individual price than the first mortgage, but that price applies only to the second balance. The old first mortgage keeps its low interest cost on everything it still covers.

A refinance works the other way. The new loan replaces the whole balance, so its pricing applies to every dollar, including the dollars that were cheap before.

Run the weights with percentages of value. Say the first mortgage sits at 45% of the property’s value and the investment ceiling is 70% CLTV. That leaves 25 points of value as headroom. If the line is fully used, it makes up roughly 36% of the combined debt, and the first mortgage makes up the other 64%. The higher price touches about a third of the debt, and the low first mortgage still carries the rest.

Now compare that with a cash-out refinance on the same property. A cash-out refinance on a standard investment property tops out around 75% LTV across most of the network, and about six months of seasoning is the common expectation. The new pricing would apply to 100% of the new balance. If the first mortgage is far cheaper than what a new first would cost, the refinance reprices the larger piece of the debt, and that usually decides the comparison.

Three things push the blend one way or the other:

• How large the line is compared with the first balance.
• How much higher the line’s pricing sits above the first mortgage.
• How many fixed fees the line carries relative to its size.

The Cost Stack, Piece by Piece

Every line has the same cost parts, and each one should be written down before anyone compares offers.

• Interest on the drawn balance. It floats. Investment lines in the network use a five-year interest-only draw, then a 25-year fully amortizing repayment, and the pricing floats across both periods.
• Origination and closing charges. These are usually fixed or tied to the line, not to the old first balance.
• Valuation. Lines at or below $500,000 ordinarily run an automated valuation with no traditional appraisal. A higher CLTV may require a secondary valuation, and a borrower may ask for a full appraisal at any size.
• Annual or inactivity charges. These vary by lender, so they should be requested in writing from any lender before comparing offers.
• Draw behavior. At least 75% of the line is drawn at closing, so the line is closer to a lump-sum second loan than a standby cushion. Later draws carry a $1,000 minimum, except Texas at $4,000.

The general pattern holds. A cash-out lender usually charges full mortgage closing costs on the whole new loan, while a line lender’s charges are tied to the line.

How Underwriting Treats the Line, Step by Step

On a typical file, the review runs in this order.

1. Lien position. The line is junior or senior depending on how it is structured. In second position, it is paid after the first lender in a sale or foreclosure, which is why the lender sizes it so carefully.

2. Combined loan-to-value. The lender adds the existing first balance to the requested line and divides by the property’s value. On an investment property, the network’s ceiling is 70% CLTV, no exceptions.

3. Credit. An investment line has a 700 minimum credit score. The score comes from a single-bureau model keyed to the primary wage earner, and the report can be no more than 90 days old at closing.

4. Debt-to-income. DTI is capped at 50%. The line is qualified on an interest-only payment calculated on the maximum draw, and every financed property counts toward DTI regardless of who holds title.

5. Vesting. Title must sit with the individual borrower or an inter vivos revocable living trust.

6. Exposure. A borrower is limited to three lines, and anyone with more than 15 financed properties is not eligible.

7. Property. Single-family, 2-4 units, PUDs, townhomes, and condominiums, including non-warrantable condos, are eligible. Manufactured homes, co-ops, condotels, log homes, commercial, mixed-use, and agricultural-zoned properties are not offered.

None of this looks at rent. That is the sharpest difference from a DSCR loan, which qualifies primarily on property-level rental income covering the payment, subject to lender guidelines.

Headroom Comes Before Fees

Line size comes first because it controls everything after it. The formula is simple: property value times the CLTV ceiling, minus the first mortgage balance, capped at the line limit.

On an investment property, the ceiling is 70% CLTV and the line cap is $500,000. A first mortgage at 60% of value leaves only 10 points of headroom. A line that small spreads its fixed fees over a thin balance, so the true cost of the new money climbs. A first mortgage at 40% of value leaves 30 points, and the same fixed fees spread across a much larger line.

Occupancy changes the ceiling, so the occupancy has to be stated before any figure is used. On a primary residence in the same network, the ceiling reaches 90% CLTV only at a 720-or-better credit profile and up to $500,000, and a 700-plus profile reaches 85%. Those tiers do not apply to an investment property. An investor who quotes a primary-residence ceiling for a rental is working from the wrong table.

(Honestly, this is where most cost comparisons go wrong. The line’s price is the last thing to look at, not the first.)

Second Lien vs Cash-Out Refinance

A DSCR cash-out replaces the low first and tests rent against the full housing payment. That makes it a different product, not a cheaper version of the same one. The complete DSCR loans guide explains how that coverage test works.

A note on the coverage number: 1.00 is where many select programs start, and a separate select-lender path takes coverage below 1.00 with leverage and terms adjusted. Clearing 1.00 does not mean the property produces positive cash flow, because repairs, vacancy, management, utilities, and capex all sit outside the calculation.

For the full side-by-side on what a rental line can save, see Lendmire’s piece How Much a Rental HELOC Saves Over Replacing a Low First Mortgage.

Payment Shock: Draw Period to Repayment

Cost is not a static number on this product. The payment changes as the line moves through its phases.

The CFPB’s consumer HELOC booklet describes the basic structure. A HELOC usually carries a variable price built from an index plus a margin, some plans start with a low introductory price that lasts a short time, and many plans allow interest-only payments during the draw period. The same booklet notes that lenders can freeze or reduce a line if the home’s value falls or the borrower’s finances worsen. It is written for consumer lines on a borrower’s home, so treat it as general background rather than a description of investment-property terms.

For an investment line in the network, the practical stress test has two steps.

First, price the interest-only draw period using the post-introductory margin, not any teaser. Second, price the amortizing repayment period, when principal joins the payment and the balance is spread over 25 years. The payment in the second phase is the one that matters for a long hold. If the index rises, both phases rise with it, because the pricing never converts to fixed.

Because the lender qualifies the file on an interest-only payment at the maximum draw, the approval test reflects the first phase, not the second. A borrower who plans to carry the line past the draw period should model the repayment phase on their own.

Where the General Rule Breaks

The blended-cost logic holds on most files. Several edge cases change it.

• Lender scarcity. Many large retail lenders decline second-position lines on rentals altogether. In practice, the question on many files is not which line is more affordable but who will write one. A wholesale network that sees many lenders’ guidelines can find the lenders who will.
• A line on the primary residence. A common workaround is a line against the investor’s own home, with the money deployed into the rental. That line is underwritten on the primary-residence tiers, not the investment tiers, and it puts the investor’s home behind the debt.
• A first-lien line on a mortgaged property. In the network, a first-lien line on a property that already has a mortgage pays that off and replaces it. An investor protecting a low first must choose second position deliberately.
• A later refinance. A second lien has to be paid off or dealt with before a cash-out refinance on that property can happen. For a BRRRR exit, the line works better as a bridge than as the plan for the end of the deal.
• Two-to-four units. Living in one unit puts the borrower in the primary-residence tier. Renting every unit puts the borrower in the investment tier, with its 70% CLTV ceiling.
• LLC-owned rentals. LLCs, corporations, partnerships, and irrevocable, blind, or land trusts cannot hold title on these lines. A property already deeded to an LLC needs a vesting change, or a DSCR cash-out refinance subject to program terms.
• Mixed-use draws. Money drawn for the rental and money drawn for personal use are not treated alike for tax purposes. Tax treatment can depend on how the funds are used and how the property is held; investors should keep clear records and speak with a qualified tax professional before relying on any deduction. IRS Publication 527 covers rental property interest.

When the Refinance Wins

The line is not always the right tool. A refinance tends to win in four situations.

• The first mortgage is not actually low, so there is little interest cost to protect.
• The investor needs more leverage than a 70% CLTV investment ceiling allows.
• The borrower’s debt-to-income ratio is too high for a line, but the rent comfortably covers a new first mortgage.
• The property is held in an LLC and a vesting change is not practical.

Leverage stacking matters too. A second lien adds debt against the same asset, and a bad outcome on the next rental can reach the property securing the line. The CLTV test caps the lenders’ exposure, but it does not cap the investor’s.

What the Decision Looks Like in Practice

A workable decision follows three steps. First, compute headroom: value times 70%, minus the first balance, capped at $500,000. Second, compute the weights: the share of combined debt the new line would represent. Third, compare the line’s fixed fees and post-introductory pricing against a cash-out refinance’s full closing costs over the planned hold.

If the line is a meaningful share of the combined debt and the hold is long, the refinance may close the gap. If the line is a small share of the debt and the first mortgage is much cheaper than a new one, the line usually wins. The calculator on this page is an illustrative estimate only and does not replace written quotes.

Lendmire’s HELOC lines are available in its 16 full-service states, a narrower footprint than its DSCR investor programs, which cover 41 markets, including Washington, D.C. Lendmire brokers these files through select wholesale partners and does not lend directly.

Key Terms Defined

Second lien: A loan recorded behind the first mortgage that is paid only after the first lender in a sale or foreclosure.

Combined loan-to-value (CLTV): All loans on the property added together and divided by the property’s value.

Draw period: The early phase of a line, during which payments can be interest-only.

Repayment period: The later phase, when principal and interest are both due.

Index and margin: The two parts of a variable price: a published benchmark plus the lender’s added percentage.

DSCR: Monthly rent divided by the full monthly housing payment, which tests the property instead of the borrower.

Next Steps

If you are considering a home equity line and want to see how the numbers work, Lendmire can help you compare HELOC options based on the property, the equity available, credit profile, combined leverage, and your goals. Reach the team at 828-256-2183 or request a quote through the quote page.

A cheap first mortgage is worth more the longer the hold, so the line’s real cost depends on how long the investor keeps both loans.

About Lendmire

Lendmire, NMLS# 2371349, is a mortgage brokerage that arranges home equity lines of credit through wholesale lending partners in its 16 full-service states. Lines on primary residences, second homes and investment properties are each reviewed individually by the lender under the program’s occupancy, credit and combined-loan-to-value guidelines. Scotsman Guide named Lendmire a Top Mortgage Workplace in both 2025 and 2026.

References

1. CFPB: What you should know about home equity lines of credit

2. IRS Publication 527: Residential Rental Property