The Quick Read: A homeowner with a low first mortgage saves by repricing only the new money. A cash-out refinance reprices every dollar of the existing balance, while a home equity line of credit (HELOC) leaves the first mortgage alone. The saving is roughly the first balance times the rate gap, minus the HELOC’s premium on the draw and any refinance costs.
- The first mortgage keeps its balance, rate and term when you add a HELOC. A cash-out refinance replaces all three.
- The saving shrinks as the draw grows relative to the first balance, and it shrinks when your old first is only modestly below market.
- On this network, an investment-property line caps at 70% combined loan-to-value (CLTV) and $500,000. Primary-residence lines reach 90% CLTV only at a 720-or-better credit profile.
- Pricing on these lines floats and never converts to fixed, so a rising index erodes the saving.
- Clearing the HELOC math says nothing about rental cash flow. That is a separate test.
Lenders call this the lock-in effect: owners hold a cheap first mortgage and do not want to give it up. Wolf Street’s analysis of a federal mortgage database puts 49.9% of $12.3 trillion in unpaid principal in the lowest-rate tier it tracks. The same author’s earlier update shows that tier topped 65% at its peak. It is fading slowly.
How large a line the equity supports.
An equity line is sized by combined loan-to-value, occupancy, and credit — not by rental coverage. Switch the occupancy or the credit band and the ceiling moves with it.
Investment-property lines require a 700 minimum credit score; second-home lines start at a 640 minimum and primary-residence lines at 600, and the combined-LTV ceiling steps down as the credit band drops on primary-residence and second-home lines and holds on investment-property lines; the line cap steps down on primary-residence lines and holds at every tier on investment-property and second-home lines.
A debt-to-income ratio above 45% requires 680+ credit. Profiles under 640 are limited to single-family homes. At least 75% of the approved line is drawn at closing. Ceilings, floors, and caps update from Lendmire’s centralized guideline source.
Line estimate
Illustrative estimate only — not a quote, Loan Estimate, approval, or commitment to lend. The rate is an editable assumption; equity-line pricing is variable through both the draw and repayment periods and never converts to fixed. Occupancy and credit drive the ceiling together: an investment property tops out at 70% combined LTV (minimum credit 700, line cap $500,000); a second home tops out at 90% combined LTV (minimum credit 640, line cap $500,000), with the ceiling stepping down as the credit band drops (the cap holds at every tier); a primary residence tops out at 90% combined LTV (minimum credit 600), and its $750,000 maximum line is available only at 75% combined LTV or below with a 700-or-better credit profile (720 on the longer-runway program) and a full appraisal. Lines above $500,000 require a full appraisal. Credit, debt-to-income, property type, and full underwriting review all affect the final line.
If you hold one of those loans and need cash for a rental down payment or a renovation, that low first is an asset. This guide shows how to put a number on it.
What Does Keeping the First and Adding a HELOC Actually Mean?
You leave the existing first mortgage untouched and open a separate line of credit behind it. That line is a second lien, a claim on the property that ranks behind the first. You draw what you need, and only that draw carries the HELOC‘s price.
The alternative is a cash-out refinance. A new, larger loan pays off the old first and hands you the difference. Every dollar, including the balance you already owed, is now priced at today’s level.
| Factor | Keep first + HELOC | Cash-out refinance |
|---|---|---|
| Existing first mortgage | Stays in place | Paid off and replaced |
| What gets repriced | Only the new draw | The whole balance |
| Pricing behavior | HELOC floats | New loan’s terms |
| Closing costs | On the line only | On the full new loan |
| Main risk | Floating-price drift | Losing the cheap first |
The HELOC is a standalone line, and it can sit in first or second lien position. When you keep a low first, it sits in second position.
The Savings Formula, Step by Step
The saving is the cost of repricing everything minus the cost of the keep-the-first path. Write the first balance as F, the draw as D, the old first rate as r, the cash-out rate as c, and the HELOC rate as h.
- Replace path: you pay c on F plus D.
- Keep path: you pay r on F and h on D.
- Annual saving: F × (c − r) minus D × (h − c), then minus any extra closing costs on the refinance side.
That is two terms in plain words. The first is the benefit of not repricing your old balance. The second is the penalty for paying a higher price on the new money through the HELOC.
Do not average the two rates. A simple average ignores the balance sizes. A weighted blend is the right measure: each rate counts in proportion to its share of total debt. If the first is 90% of total debt, the old rate sets 90% of the blend. At 50/50, it sets half.
Where the Crossover Sits
The keep path wins as long as F × (c − r) is bigger than D × (h − c). Rearranged, the HELOC loses only when its premium over the cash-out price exceeds the old-first discount divided by the draw-to-first ratio.
Here is that threshold. Treat it as a model, with the same cash raised on both sides, the same holding period, and closing costs and principal paydown ignored.
| Draw as share of first balance | HELOC premium needed to lose |
|---|---|
| 10% | 10× the first’s discount |
| 25% | 4× the first’s discount |
| 50% | 2× the first’s discount |
| 100% | 1× the first’s discount |
Run the numbers on a 25% draw. Say a homeowner’s first sits well below today’s cash-out pricing. The HELOC would have to cost four times that gap above the cash-out price before a refinance wins. That almost never happens, which is why small draws favor the line so strongly.
Flip it around. If your first is only a little below market, the discount is small. A modest HELOC premium then wipes it out. This is the most common way the keep path loses.
The Five Inputs That Decide Your Number
1. The rate gap. The wider the distance between your old first and a new cash-out, the more repricing costs you.
2. Draw size against first balance. A small draw on a big first is the sweet spot.
3. The HELOC’s premium over what a cash-out would charge on the same new money.
4. Costs on each path. A refinance carries closing costs on the whole loan. The line carries costs on the line.
5. Rate drift. Your fixed first cannot reprice, but the HELOC can.
Notice what is missing: the size of your equity. Equity decides whether you can borrow at all. It does not change which path is cheaper per dollar.
How Much Line Will Your Equity Support?
Your line equals value times the lender’s combined-loan-to-value ceiling, minus every lien already on the property, capped at the program maximum. The CFPB’s HELOC booklet walks through the same method with a worked example.
Across the wholesale network Lendmire places HELOC files with, the ceiling depends on how you occupy the property:
- Primary residence: 90% CLTV exists only at a 720-or-better credit profile, on lines up to $500,000. A 700+ profile reaches 85% CLTV up to $500,000. Lines up to $750,000 are available at 75% CLTV with a 700+ score.
- Second home: up to 90% CLTV at 720+, with a $500,000 maximum line.
- Investment property: 70% CLTV, a 700 minimum credit profile, and a $500,000 maximum line. There is no tier above that.
Picture a primary residence where the first mortgage equals 60% of value and your profile is 720+. A 90% ceiling leaves room for a line of up to 30% of value, subject to the $500,000 cap. On a rental at 70% CLTV, a first at 50% of value leaves up to 20% of value.
Many bank and credit union lines you will see advertised use other ceilings. Those describe the broader market. They do not apply to this network.
One feature matters for your savings math. At least 75% of the line is drawn at closing. You pay on the drawn balance from day one, so size the line to your actual need rather than your maximum.
How Underwriting Treats a HELOC, Step by Step
A HELOC is reviewed on you. A DSCR loan is reviewed on the property.
1. Collateral and title. The line must be held by an individual or a revocable living trust. LLCs, corporations and partnerships cannot hold title. A rental already deeded to an LLC needs a vesting change, or a DSCR cash-out refinance instead.
2. Credit. The floor is 600 for primary residences, 640 for second homes and 700 for investment properties. The score model is single-bureau, keyed to the primary wage earner.
3. Debt-to-income (DTI). The maximum is 50%, and 45% for profiles from 600 to 679. A ratio above 45% requires a 680 minimum. The lender reviews your file on the interest-only payment calculated at the maximum draw, not the amount you plan to take.
4. Valuation. Lines at or below $500,000 ordinarily run automated valuation with no traditional appraisal. A full appraisal is required above $500,000, and you can request one in any case.
5. Recording. The line records behind your first. The first mortgage’s own documents govern whether it allows a junior lien, so read them before you apply.
Investors collide with that DTI step often. A borrower with many financed properties can hit the personal-DTI ceiling long before the rents run out. Exposure rules apply as well: a borrower is limited to three lines, and an owner of more than 15 financed properties is not eligible. HELOC lines are also available in far fewer states than the DSCR footprint, so check availability first.
Draw and Repayment: What the Structure Looks Like
Under the CFPB’s description of a HELOC, you borrow against an open-end line during a draw period, then repay. On primary residences and second homes, two structures exist:
- A 3-year interest-only draw followed by a 17-year fully amortizing repayment.
- A 5-year interest-only draw followed by a 25-year fully amortizing repayment.
Investment lines use the 5-year draw and 25-year repayment structure only.
Interest-only feels cheap during the draw. Payments then jump when amortization starts, because you begin repaying principal. Plan for that step.
Pricing floats across both the draw and the repayment period and never converts to fixed. The CFPB’s HELOC booklet notes that these lines typically tie to a public index plus a margin, and that variable-rate plans secured by a dwelling must carry a lifetime cap. Its HELOC brochure adds that payments can change even if you draw nothing more.
That floating price is the main weakness of the keep path. It is why a rate-rise stress test belongs in your math. Raise h by a few steps and watch D × (h − c) grow. A small draw on a big first absorbs the shock. A large draw does not.
After closing, the minimum for each additional draw is typically $1,000 on the longer-runway structure, with exceptions by state.
Where the General Rule Breaks
Keeping the first usually wins. These cases are where it does not:
- Your first is barely below market. The discount is small, so a modest HELOC premium erases it.
- The draw is large against the first. At a 100% draw-to-first ratio, the premium only has to match the discount.
- The rental sits in an LLC. The line cannot be held there. A DSCR cash-out refinance, at about 75% LTV on a standard rental with around 6 months of seasoning, becomes the realistic route.
- You need more than the line allows. An investment line caps at $500,000 total.
- You need a fixed price. These lines float, so someone who wants payment stability should consider a single fixed-term loan.
- A DSCR first is already on the rental. Adding a second lien changes the combined obligation, and the first lender’s documents decide whether a junior lien is allowed at all. Some products labeled DSCR HELOC replace the first mortgage, which makes them a cash-out refinance in disguise. Ask which one you are being offered.
- A later refinance of the first. A junior lienholder has no obligation to subordinate, so a future refinance of the first may require paying the line off.
On primary-residence lines, bankruptcy requires 4 years of seasoning from discharge or dismissal. Foreclosure history is handled differently across the network. Investment files follow a 7-year seasoning path for foreclosure and 4 years for a deed-in-lieu, pre-foreclosure or short sale.
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.
Putting HELOC Cash to Work on a Rental
A common reason a lock-in owner wants this cash is a down payment on the next rental. The two loans then sit side by side, and each is tested differently.
Across most programs on the network, a DSCR purchase lands at 75%–80% LTV on a purchase, meaning 20%–25% down. Select programs reach 85% LTV (15% down) with roughly a 700+ score. Credit expectations typically start around 660, with a 620 floor in parts of the network and the strongest leverage at 700+.
DSCR loans are designed for non-owner-occupied investment properties. Because they are business-purpose investor loans, they are reviewed differently from a standard owner-occupied mortgage. The property qualifies primarily on rental income covering the payment, subject to lender guidelines.
Coverage works like this: monthly rent divided by principal, interest, taxes, insurance and any HOA dues. A 1.00 is where many select programs start. A separate select-lender path takes coverage below 1.00, with leverage and terms adjusted. Stronger ratios open better pricing and leverage.
One caution. A ratio above 1.00 is not positive cash flow. Repairs, vacancy, management, utilities and capex all sit outside the calculation.
Then add the HELOC payment to your own personal picture. It counts in your DTI, not in the rental’s coverage ratio. Strong files clear both tests: enough equity and enough rent.
For a fuller look at how the rental side is reviewed, see the complete DSCR loans guide. Lendmire has also compared a rental HELOC against replacing a low first mortgage in detail.
Keep the First If, Replace It If
Keep the first and add a line when:
- Your draw is small relative to the first balance.
- Your first sits well below what a new loan would cost.
- You can hold title individually or in a revocable trust.
- You can stomach a floating price and a payment step-up after the draw.
Replace the first when:
- Your first is only modestly below market.
- You need a large sum against a small first.
- The property is held in an LLC, subject to program terms.
- You want a single fixed-term loan with one payment.
Lendmire’s piece How Much a Lock-In Landlord Saves With a Rental HELOC Over a New First works through the same decision for property already owned as a rental.
Key Terms Defined
Lock-in effect: The reluctance to give up a low-priced mortgage, which keeps owners in place and makes a replacement loan costly.
HELOC: An open-end line of credit secured by your property, which you draw on and repay during a set period.
CLTV: Combined loan-to-value, the sum of all liens divided by the property’s value.
Second lien: A loan recorded behind the first mortgage that is repaid after the first if the property is sold or foreclosed.
Draw period: The stretch when you can borrow from the line, often paying interest only.
Blended rate: The weighted average cost across two balances, each counted by its share of total debt.
DSCR: Debt service coverage ratio, a rental’s monthly rent divided by its monthly principal, interest, taxes, insurance and HOA dues.
Frequently Asked Questions
Is it cheaper to keep a low first and add a HELOC than to refinance?
Usually, when the draw is small compared with the first balance and the first sits well below market. The saving is the first balance times the rate gap, minus the HELOC’s premium on the draw. It narrows or flips when the first is near market or the draw is large.
Can I get a HELOC on a rental property?
Yes, on this network, on an investment property held by an individual or a revocable living trust. Investment lines require a 700 minimum credit profile, cap at 70% CLTV and $500,000, and use the 5-year draw and 25-year repayment structure. Availability is limited to a narrower set of states than the DSCR footprint, and every file is reviewed individually.
Does the HELOC rate apply to my whole debt?
No. Only the drawn amount carries the HELOC’s price. Your first mortgage keeps its own rate, and the number to compare is the blend across both balances, weighted by size.
What happens to the saving if the index rises?
It shrinks. A floating line reprices even if you draw nothing more, and these lines never convert to fixed. Test the math with a few higher steps before committing.
Does a DSCR cash-out refinance make sense instead?
It can, particularly when the rental is held in an LLC or when you need more than a line allows. A cash-out on a standard rental generally tops out around 75% LTV with about 6 months of seasoning expected. You give up the old first in exchange.
About Lendmire
Lendmire (NMLS# 2371349) is a mortgage broker. It arranges DSCR investor loans across 41 markets, including Washington, D.C., through select lenders in its wholesale network. Its HELOC lines are available only in 16 states. Lendmire is never the lender, and every figure here is subject to lender guidelines and full file review. Nothing here is a commitment to lend. Scotsman Guide named Lendmire a Top Mortgage Workplace in both 2025 and 2026.
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. Call 828-256-2183 to talk through your file.
Many owners holding a cheap first will find that the smaller their draw, the more the old mortgage is worth keeping.
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References
1. Wolf Street – lock-in update
2. Wolf Street – lock-in fades slowly
3. CFPB / Federal Reserve – HELOC booklet
This article is part of Lendmire’s home equity line of credit program — full qualification details, guidelines, and scenarios live on the program page.
Related reading: How Much a Lock-in Homeowner Saves Adding a HELOC Over a New First · How Much a Lock-in Landlord Saves With a Rental HELOC Over a New First · How Much a HELOC Saves on Card Debt When You Keep Your First
Brandon Miller
Founder & CEO, Mortgage Loan Originator, Lendmire LLC
- Mortgage Loan Originator · NMLS# 1129696 · Verify on NMLS Consumer Access
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Legal disclosures. Lendmire (NMLS# 2371349) is a state-licensed mortgage brokerage that arranges financing through wholesale lender relationships. Lendmire is not a direct lender, depository institution, or registered financial advisor. The discussion above is general informational content about real estate financing — it is not financial, legal, or tax advice, and readers should consult licensed professionals for guidance on their individual circumstances. Loan inquiries are subject to lender underwriting; this article does not represent a commitment to lend. Loan terms, rates, and qualification standards vary by borrower, property, and state, and are subject to change at any time. Equal Housing Opportunity. NMLS Consumer Access: nmlsconsumeraccess.org.