The Quick Read: DTI math stacks three housing obligations in one ratio: the old home’s payment, the HELOC payment, and the new mortgage payment, all divided by gross monthly income. The result decides whether a DTI-based purchase loan works while you hold both homes. A DSCR purchase skips this personal ratio and tests the rental’s income instead.
- Add the old mortgage, the HELOC payment, the new payment, and other recurring debts, then divide by gross monthly income.
- The HELOC payment lenders count varies by program, so confirm which one applies before you plan.
- Removing the old home’s payment, through a documented sale or lease, is usually the biggest swing in the ratio.
- On Lendmire’s network, a HELOC is tested on an interest-only payment calculated on the maximum draw, not the amount you plan to draw.
- A DSCR purchase of a rental runs on rent coverage, though credit, reserves, and property eligibility still apply, subject to lender guidelines.
Bridging homes with a HELOC means borrowing against the home you own to fund the next one. The risk sits in the ratio. Most files that fail do so because the borrower counted two payments and the lender counted three. This article walks the arithmetic line by line, shows where the common rule breaks, and covers what it means if the next property is an investment.
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.
Key Terms Defined
DTI (debt-to-income ratio): All monthly debt payments divided by gross monthly income.
Gross monthly income: Income before taxes and deductions, which is the denominator.
HELOC: A revolving line of credit secured by a home, usually with a draw period and a repayment period.
CLTV (combined loan-to-value): All liens on a property added together and divided by its value.
PITIA: Principal, interest, taxes, insurance, and association dues, the full monthly housing obligation.
DSCR (debt service coverage ratio): Monthly rent divided by the property’s PITIA. It tests the rental, not the borrower’s paycheck.
What the DTI Formula Actually Measures
The CFPB defines DTI as all monthly debt payments divided by gross monthly income. Its example: $2,000 of monthly debt on $6,000 of gross income is 33%. The same page notes that different loan products and lenders set different limits. There is no single ceiling that applies to every loan.
So the first job is to know which product you are being underwritten for. A conventional purchase has a DTI limit. A HELOC has its own. A DSCR loan doesn’t test your personal DTI at all.
Within the formula, “debt” means recurring obligations: housing payments, auto loans, student loans, minimum card payments. It does not include groceries or utilities.
Step 1: Build the Numerator
Start with every monthly obligation the lender will see at the moment it tests the file.
1. Old home housing payment. Use the full PITIA on the home you are keeping or still own. If you plan to sell, it stays in until the sale is documented.
2. HELOC payment. This is the new line against the old home. Step 2 covers which payment counts.
3. New home payment. The proposed PITIA on the property you are buying.
4. Other recurring debts. Car payments, student loans, card minimums.
Add them. That total is the top half of the ratio.
Step 2: Decide Which HELOC Payment Counts
This is where files go wrong, because programs treat the line differently. Three conventions exist.
First, some underwriting counts only the minimum or interest-only payment on the drawn balance. Second, some lenders apply an overlay that uses the payment on the full line even when you draw part of it. Third, when no payment is documented at all, agency guidelines use a fallback. Freddie Mac’s Seller/Servicer Guide requires HELOC payments in monthly DTI when there’s an outstanding balance, and assumes a payment when none is documented. That’s agency material, shown here only as contrast. It doesn’t govern investor loans.
Across Lendmire’s wholesale network, the home equity line is qualified on an interest-only payment calculated on the maximum draw. A planned partial draw does not shrink the tested payment. If you open a large line and draw a small piece, the ratio still reflects the large line.
An undrawn line is not a zero. Treat any open line as a payment until the specific lender tells you otherwise.
Step 3: Run the Two-Home Versus One-Home Comparison
Use your own numbers, but the shape is consistent. Take gross monthly income as the denominator. Compute DTI three ways:
1. Today: old payment plus other debts, no HELOC yet.
2. Overlap: old payment plus HELOC payment plus new payment plus other debts.
3. After the sale: HELOC paid off, old payment gone, new payment plus other debts.
The overlap line is the one a purchase lender tests if you are buying before selling. It is almost always the highest. The after-sale line is the lowest, and it only counts if the sale is documented as a signed contract or closed transaction.
On a modest-income scenario, carrying both homes pushes DTI into the low 40s. Removing the old payment pulls it into the high 20s. The old home’s payment is the swing item. The HELOC adds to it during overlap and disappears at payoff.
Two other habits help. Run the overlap line at the full-line payment, since that’s the conservative convention. Then run it at the drawn payment so you can see the cushion between the two.
Step 4: Document the File
Typical items a lender asks for:
- The HELOC agreement and the most recent statement.
- Sourced and seasoned down-payment funds. A BiggerPockets investor thread advises drawing early enough that the deposit doesn’t appear as a recent large deposit on the last two months of statements.
- Evidence of a listing or a signed sale contract, if you want the old payment removed.
- A lease, if the old home becomes a rental and rent is used to offset its payment.
Documentation is where preventable gaps pile up. A missing statement or an unsourced deposit pends a file the same way a bad ratio does.
Reverse Math: Solve From the Ceiling
You can also work backward. Take the DTI limit for the product, multiply by gross monthly income, and you have the maximum total monthly debt. Subtract the old payment, the new payment, and other debts. What remains is the room left for the HELOC payment.
On the HELOC itself, Lendmire’s network allows a maximum DTI of 50%. Profiles with credit from 600 to 679 are held to 45%. A ratio above 45% requires a 680 minimum. These limits are subject to lender guidelines and full file review.
If the room left is smaller than the tested payment, you have four levers: a smaller line, paying off another debt, adding income through a co-borrower, or a lower purchase price. Each one moves the ratio in the direction you expect, and you can rerun the three-way comparison to see by how much.
Timing: Open the Line Before You List
NerdWallet’s guide to buying and selling at the same time notes that a lender generally won’t approve a HELOC after the home is listed for sale. The line has to be in place first. Approval also takes a while, and it can run longer than a first mortgage.
On Lendmire’s network there’s a related rule: in several states a property listed for sale, or listed within the past 60 days, is ineligible for the equity line. Listing first and borrowing second often doesn’t work.
Where the General Rule Breaks
The stacking rule is the default. These cases bend it.
DSCR purchase of the next property. If the next property is a rental, the purchase can run through a DSCR loan. It qualifies primarily on property-level rental income covering the payment, subject to lender guidelines, rather than personal DTI. Your HELOC payment isn’t a factor in that test. Credit, reserves, and property eligibility still apply. This is why investors with maxed-out DTI often move to DSCR. As one BiggerPockets reply puts it, DSCR is the scaling route when DTI is maxed, at the cost of cash flow.
Coverage is not cash flow. DSCR compares rent to PITIA only. Clearing 1.00 does not mean the rental pays you after the HELOC payment sits on top. Repairs, vacancy, management, and utilities sit outside the calculation. A select group of programs starts at 1.00. A separate select-lender path takes coverage below 1.00, with leverage and terms adjusted.
The HELOC is a DTI product itself. Even when the purchase is DSCR, the line is underwritten to the borrower, not to the rent. Credit, DTI, and valuation all apply to the line.
Titling. On Lendmire’s HELOC programs, an LLC cannot hold title. Fee simple or leasehold held by the individual or a revocable living trust is the standard. A rental already deeded to an LLC points toward a DSCR cash-out refinance instead.
No second-lien DSCR. A DSCR loan generally can’t sit behind another loan, so a HELOC on the same rental you’re buying doesn’t pair with it.
Bridge loans. Some bridge programs may let the departing home’s payment be excluded from DTI, depending on program and sale status. That varies by program. A bridge loan is a lump sum built for buying before selling, while a HELOC is a revolving line.
HELOC on the new property. A piggyback structure means paying all three loans while the old home is on the market.
The Parameters That Shape the HELOC Side
Occupancy changes the numbers, so state the property type before quoting any ceiling.
| Property | Max CLTV | Max line | Credit floor |
|---|---|---|---|
| Primary residence | Up to 90% (720+ only) | $750,000 | 600 |
| Second home | Up to 90% (720+ only) | $500,000 | 640 |
| Investment property | 70% | $500,000 | 700 |
Subject to lender guidelines. A line above $500,000 is primary-residence only and requires 700 or better (720 on the longer-runway structure), with a full appraisal. Most lines at or below $500,000 use automated valuation. At least 75% of the line is drawn at closing, and the line is a standalone first or second lien. Lendmire’s HELOC availability covers its 16 full-service states, which is narrower than its DSCR footprint.
Notice what that means for bridging. If your old home is your primary residence, the line can be sizable. If you’re drawing against a rental, the ceiling drops and the credit floor rises.
What the Investor Decision Looks Like
An investor with a primary home, a low first mortgage, and strong equity has a choice. Draw on the line and buy conventionally, or draw on the line and buy through DSCR.
On the conventional route, the three-way stack decides everything. The old payment and the HELOC payment both stay in until the sale is documented.
On the DSCR route, the purchase is tested on rent coverage. The HELOC still has to clear its own DTI test, but the new property’s loan doesn’t add to your personal ratio. Another BiggerPockets reply warns that funding the whole down payment from a HELOC leaves the investor fully leveraged and squeezes cash flow. That’s a real cost.
A HELOC also puts the primary home at risk if the plan fails. If the rental underperforms and the line is fully drawn, the collateral is where you live.
For purchases, most DSCR files on the network land at 75% to 80% LTV, with select programs reaching 85% at around a 700 score. A bigger down payment lowers the payment and lifts coverage, but it doesn’t remove credit floors, reserve rules, or property eligibility. Reserves vary by lender, leverage, and loan size, and commonly run around six months of PITIA. For more on how the program works, see Lendmire’s complete DSCR loans guide.
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.
Common Mistakes on These Files
- Counting the undrawn line as zero. Lenders often don’t.
- Assuming a partial draw lowers the tested payment. On this network it doesn’t.
- Subtracting the old payment before the sale is documented. A plan to sell is not a sale.
- Opening the line after listing. It generally can’t be done.
- Letting the deposit land late. An unseasoned, unsourced deposit pends the file.
- Treating 1.00 coverage as profit. Coverage and cash flow are different numbers.
Frequently Asked Questions
Does an undrawn HELOC count against DTI?
Often yes. Some lenders count a payment as soon as the line exists, and some use the payment on the full line. Others count only the drawn balance. On Lendmire’s network, the line is tested on an interest-only payment on the maximum draw.
Can the old mortgage payment be left out of the ratio?
Sometimes. A documented sale, such as a signed contract or closing, can remove it. A lease can offset it if the old home becomes a rental. A plan to sell, with nothing signed, usually doesn’t count.
What if the home doesn’t sell?
Then all three payments continue. That’s the core risk of bridging. Run the overlap ratio with extra months of carry before you commit, and keep enough equity after the draw to cover sale costs.
Does a DSCR loan check my personal DTI?
A DSCR purchase is reviewed primarily on the rental’s income covering the payment, subject to lender guidelines, so personal DTI isn’t the test. Sub-1.00 coverage is available through select lenders in the network, with leverage and terms adjusted.
Can I use the line for a down payment on a rental?
Often, yes, as long as the funds are sourced and seasoned. The deposit has to trace to the line, and the line must clear its own DTI and credit tests. If you 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, with a quote available through the Lendmire quote page.
About Lendmire
As a mortgage broker (NMLS# 2371349), Lendmire helps homeowners and real estate investors in its 16 full-service states open home equity lines of credit arranged through wholesale lenders. Lendmire is never the lender; line amounts, ceilings and terms are set by the lender under its guidelines. Scotsman Guide named Lendmire a Top Mortgage Workplace in both 2025 and 2026.
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References
1. CFPB – What is a debt-to-income ratio?
2. Freddie Mac Seller/Servicer Guide, Section 5401.2
3. BiggerPockets – Using a HELOC for investment property down payment
4. NerdWallet – How to Buy and Sell a House at the Same Time
5. BiggerPockets – How to finance a property with maxed-out DTI
6. BiggerPockets – Using a HELOC to purchase another investment property
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: HELOC Tiers for a First-Time Equity Borrower on a Primary Home · How a HELOC Funds Four Years of Tuition for a Parent Borrower · How Much Home a First-Lien HELOC Down Payment Supports After DTI
Brandon Miller
Founder & CEO, Mortgage Loan Originator, Lendmire LLC
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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.