The Quick Read: Running the DTI math means adding the new line’s payment, sized on the full draw, to every debt you already carry, dividing by gross monthly income, and comparing the result to the lender’s ceiling, which tops out at 50% on the home equity lines the network places. The HELOC has to pass that test on its own. Your rental purchase loan may face a second test, or none.
- The line’s payment counts in your debt-to-income ratio. On the lines Lendmire’s network places, it is calculated on the interest-only payment at the maximum draw.
- The ceiling is 50%, drops to 45% for credit profiles from 600 to 679, and anything above 45% needs a 680 minimum.
- A DSCR purchase loan is reviewed primarily on property-level rental income covering the payment, subject to lender guidelines. The HELOC payment sits outside that ratio.
- Clearing the coverage test is not the same as positive cash flow. You still carry the line.
Two Tests, Not One
Most people picture one approval. There are usually two, and they measure different things.
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.
The first test is the HELOC itself. The lender looks at your income and your monthly debts. This is a personal-income test, and the new line’s payment goes into it.
The second test is the purchase loan on the rental. If it is a DSCR loan, the lender compares the property’s rent to the full monthly obligation on that loan: principal, interest, taxes, insurance, and any association dues (PITIA). Your personal DTI is not the main event there. If the purchase loan is a DTI-based loan instead, the HELOC payment and the new mortgage both go into your ratio, and the stack gets tall.
That fork is why investors with high DTI or several financed properties often end up at DSCR. The HELOC solves the cash problem. It can still create a ratio problem if the purchase loan is also scored on your income.
Key Terms Defined
Debt-to-income ratio (DTI): your total monthly debt payments divided by your gross monthly income, shown as a percentage. It is calculated on income before taxes.
Gross monthly income: what you earn each month before taxes and deductions.
CLTV (combined loan-to-value): all loans secured by the property, added together, divided by its value.
Interest-only draw period: the early years of a line when the payment covers only interest, not principal.
Qualifying payment: the payment the lender uses in your ratio. It can differ from what you actually pay later.
DSCR (debt service coverage ratio): monthly rent divided by the property’s full monthly obligation. A result of 1.00 means rent equals the payment.
Which Payments Go Where
| Item | HELOC approval | DSCR purchase |
|---|---|---|
| Current mortgage (PITI) | Counts | Not in ratio |
| Auto, student, card minimums | Count | Not in ratio |
| New HELOC payment | Counts (max draw) | Not in ratio |
| New rental mortgage | Not yet existing | Counts in PITIA |
| Projected rent | Lender-specific | Core of the test |
The “not in ratio” cells do not mean the payments vanish. They mean the formula ignores them. Your bank account does not.
How to Run the DTI Math, Step by Step
1. List every monthly debt. Include your current mortgage payment with taxes and insurance, auto loans, student loans, and card minimums.
2. Find gross monthly income. Use pre-tax numbers, and use only income you can document.
3. Estimate the HELOC payment. On the network’s lines, the lender reviews your file on the interest-only payment at the maximum draw. Size the line, not just the draw you plan to take.
4. Add the new mortgage if the purchase loan is DTI-based. If it is a DSCR loan, leave it out of your personal ratio and run coverage instead.
5. Divide the total by gross monthly income. Convert to a percentage.
6. Compare to the ceiling. The network’s ceiling is 50%. It is 45% for credit profiles from 600 to 679, and a ratio above 45% requires at least a 680 score.
7. Rerun at the repayment payment. The step-up is where plans break, covered below.
A Fail, Fix, Pass Example
Here are modeled assumptions, expressed as shares of gross monthly income so no dollar amounts are needed.
- Existing debts including your current mortgage: 30%.
- HELOC payment at maximum draw: 7%.
- New purchase mortgage on a DTI-based loan: 16%.
- Total: 53%. That is over the 50% ceiling, so this scenario fails.
Now apply levers one at a time.
- Draw and size the line smaller. The HELOC share falls to 5%. Total: 51%. Still over.
- Pay off an auto loan that takes 3% of income. Total: 48%. Under 50%, but above 45%, so the file needs a 680 minimum credit profile.
- Buy a slightly cheaper property. The new mortgage share falls to 14%. Total: 46%. Passes, still above 45%.
Order matters. Paying off a debt usually moves the ratio more than shaving a few points off the draw, and it does not shrink your down payment. Some payoffs do take time to show on the credit report, so plan them before the HELOC application, not after.
On a DSCR purchase, this stack never touches the purchase test. The HELOC test remains.
Reverse the Math: How Big Can the Line Be?
Start at the ceiling and work backward.
Room for the HELOC payment = ceiling − existing debt share − new mortgage share (if counted).
Using the example above with a 50% ceiling, 30% in existing debts, and 16% for the new mortgage, the room is 4% of income. Divide that monthly payment by the payment per dollar borrowed on an interest-only line, and you have the largest balance that fits. A smaller line means a smaller qualifying payment. This is why a modest draw on a clean file often passes where a maximum draw fails.
Equity limits the line too. On an investment property, the network’s ceiling is 70% CLTV, with a 700 minimum credit profile and a $500,000 maximum line. A primary-residence line reaches 90% CLTV only at a 720-or-better profile, up to a $500,000 line. Lower credit tiers step down from there. Most investors use the primary home, which carries the higher ceilings, and it makes the collateral your own house. Lendmire’s article, Can You Use a Primary Home HELOC as a Rental Down Payment?, covers that tradeoff.
Sensitivity: Change One Input at a Time
Same scenario, DTI-based purchase loan, shares of gross monthly income. These are modeled assumptions.
| Change | HELOC | New mortgage | Total |
|---|---|---|---|
| Base case | 5% | 16% | 51% |
| Larger draw, bigger down payment | 7% | 15% | 52% |
| Smaller draw, bigger mortgage | 3% | 17% | 50% |
| Repayment phase begins | 8% | 16% | 54% |
A bigger down payment shrinks the mortgage, but the HELOC payment grows faster than the mortgage shrinks. Here, borrowing more to put down more made the ratio worse.
Where the Rule Breaks
The 43% figure is not law. It came from the original General QM test, per the CFPB’s ability-to-repay assessment. It applied to that rule, not to every mortgage. The CFPB’s DTI explainer adds that limits differ by product and lender. Use the ceiling for the actual program.
The step-up is real. A typical HELOC runs a 10-year draw period followed by a 20-year repayment period, per Opendoor. The payment grows once principal joins it, and the pricing floats. On the network’s investment lines, the structure is a 5-year interest-only draw and a 25-year repayment. Primary residences and second homes can also choose a 3-year draw with 17-year repayment. Pricing floats through both phases and never converts to fixed. Model the repayment payment, not just the draw payment.
An undrawn line rarely stays undrawn. Some lenders count a payment on an unused line. On the network’s lines, at least 75% of the line is drawn at closing, so the undrawn-line debate mostly does not apply. Open a line only as big as you intend to use.
Borrowed funds are program-dependent. Many DSCR programs accept documented HELOC proceeds for the down payment. Some limit the borrowed share, and some want part from your own seasoned cash. Draw early enough that the money sits on your statements with a clear paper trail.
Down payment and reserves are separate buckets. Reserves are the cash left over after closing, commonly around 6 months of PITIA on a DSCR purchase. Borrowed funds may cover one bucket and not the other. Conservative rate-and-term files at modest leverage under $1,500,000 can see reserves waived, and loans above that size typically step up to about 9 months. Confirm both with the program.
Title can block the HELOC. The line must be held by you personally or by a revocable living trust. LLCs and other entities cannot hold title on these lines. A property already deeded to an LLC would need a vesting change, or a DSCR cash-out refinance, subject to program terms.
Availability is narrower. Home equity lines are placed in a smaller set of states than the DSCR footprint.
What the DSCR Side Looks Like
On the purchase loan, most files land at 75% to 80% LTV on a purchase, meaning 20% to 25% down. Select programs reach 85% LTV with roughly a 700 score. A 1.00 coverage ratio is where many select programs start. A separate select-lender path takes coverage below 1.00, with leverage and terms adjusted. Credit floors run from 620 in parts of the network to about 660 on most programs, with 700 and above unlocking the strongest tiers. Loan sizes reach up to $3,000,000 on standard programs, with smaller balances available through select lenders.
A bigger down payment lowers the payment and can lift coverage. It never erases leverage caps, credit floors, or reserve rules. The strongest files clear both tests: enough equity and enough rent coverage. The complete DSCR loans guide walks through the full qualification picture.
One thing the ratio will not tell you: clearing 1.00 is not positive cash flow. Repairs, vacancy, management, utilities, and capex sit outside the calculation. (So does your HELOC payment.) A property can pass coverage and still leave your portfolio thin each month.
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.
When to Stop and When to Proceed
Stop if your total lands above 50%, or above 45% with a score under 680. Fix the stack first.
Stop if the repayment-phase payment pushes you over the ceiling, even though the draw-phase payment passed.
Proceed if the HELOC passes at the maximum-draw payment with room to spare, the purchase program accepts documented borrowed funds, and coverage clears the program’s floor.
Sequence it: pre-qualify with the HELOC payment included, confirm the purchase lender accepts borrowed funds, then draw and season the money. Between the HELOC closing and the purchase closing, avoid new credit, new financed purchases, and cosigning. Any of them can change a ratio you just worked to fix.
For a deeper look at the funding strategy, see Lendmire’s guide Using HELOC As Down Payment For Investment Property.
Frequently Asked Questions
Does the full line or just the amount I draw count in my DTI?
On the lines the network places, the qualifying payment is the interest-only payment at the maximum draw. Since at least 75% of the line is drawn at closing anyway, size the line to what you plan to use. Lenders may treat it differently.
Does an unused HELOC count against me?
It depends on the lender. Some count an estimated payment even with a zero balance, and others do not. Do not assume an open line is invisible.
Can a high DTI still work?
Sometimes. The network’s ceiling is 50%, and a ratio above 45% requires a 680 minimum credit profile. Above 50%, the HELOC does not fit, and you would need to lower the draw or pay down debts first.
Do I include rent from the new property in my DTI?
On a DSCR loan, rent is the main test and your personal DTI is not. On a DTI-based loan, how much projected rent offsets the new mortgage varies by lender and program, so ask before assuming credit.
Does DTI affect my credit score?
Not directly. Income is not on your credit report. A new line can still change your score through the inquiry and the added balance.
Next Step
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. The calculator on this page is an illustrative estimate, not a quote. Every file is subject to lender guidelines and full review. This is not a commitment to lend.
Rental portfolios tend to stall on ratios, not on equity, so the investors who run both tests before drawing are the ones who get to buy the next property.
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.
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References
1. CFPB’s ability-to-repay assessment
2. CFPB — What Is a Debt-to-Income Ratio?
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 to Run DTI Math Before Using a HELOC to Buy a Rental · HELOC DTI Rules When the Line Funds a Full Cash Purchase · Can a Self-Employed Owner Get a HELOC With High DTI?
Brandon Miller
Founder & CEO, Mortgage Loan Originator, Lendmire LLC
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Disclosure information. Lendmire is a state-licensed mortgage brokerage under NMLS# 2371349. Lendmire is not a depository institution, direct lender, or financial advisor — all loans referenced are placed through wholesale lender partners and are subject to each lender's underwriting standards. This article is provided for general informational purposes and is not a commitment to lend, nor does it constitute financial, legal, or tax advice. Loan programs, terms, rates, and qualification standards change without notice and depend on borrower profile, property type, and the state in which the subject property is located. Equal Housing Opportunity provider. NMLS Consumer Access: nmlsconsumeraccess.org.