You can use a HELOC on your current home for a down payment on another property, and both Fannie Mae and FHA guidelines explicitly allow it. The complication is that you have to clear two underwriting reviews instead of one: the HELOC itself, and then a new mortgage lender who will treat the HELOC payment as debt you already owe. The interest is usually not deductible either, which surprises most borrowers who assume home equity debt automatically qualifies.
What the New Mortgage Lender Will Accept
Fannie Mae classifies a HELOC on your existing home as “borrowed funds secured by an asset,” an acceptable source for down payment, closing costs, and reserves on a conventional loan. The lender needs three things in the file: the terms of the HELOC, evidence that the HELOC lender is not a party to the home sale, and proof the funds have actually been transferred to you. An approved credit line on paper isn’t enough; the money has to have moved.1Fannie Mae. Borrowed Funds Secured by an Asset
If you’re also claiming the same account as cash reserves, the lender subtracts the borrowed amount plus any fees. The same equity can’t do double duty as both your down payment and your emergency cushion.
FHA loans accept collateralized loans from independent third parties, so a HELOC works, provided the HELOC lender isn’t the seller, the real estate agent, or the lender writing your FHA mortgage. Unsecured borrowing (credit card advances, signature loans) is prohibited. FHA layers on additional requirements: the HELOC payment must be included in your qualifying mortgage payment, the combined loan-to-value of the FHA mortgage plus any secondary financing can’t exceed FHA’s standard LTV limits, and the second lien can’t carry a balloon payment within ten years.2U.S. Department of Housing and Urban Development. FHA Single Family Housing Policy Handbook 4000.1
On documentation, don’t try to be clever about seasoning. Mortgage lenders review at least 60 days of bank statements and every deposit during that window needs a paper trail. Drawing the HELOC early and letting the funds sit for two months is a maneuver underwriters are trained to catch, and an unexplained large deposit raises more questions than a transparent, properly documented HELOC draw. Hand over the executed HELOC agreement, the draw statement, and evidence that the HELOC lender has no connection to the sale.
How the HELOC Payment Changes Your Qualifying Math
This is where the strategy most often breaks. The HELOC payment lands in your debt column before the new mortgage payment is calculated, so you’re starting from a higher baseline than a buyer using savings or gift funds.
For conventional loans run through Fannie Mae’s automated underwriting, the maximum total debt-to-income ratio is 50%. Manually underwritten loans cap at 36%, stretching to 45% with strong compensating factors like a high credit score and significant reserves.3Fannie Mae. Debt-to-Income Ratios If the HELOC doesn’t require monthly payments during the draw period, the lender calculates an equivalent payment and uses that figure. Interest-only or introductory-rate HELOCs get no pass; the underwriter uses the fully indexed rate, not a temporary promotional one.1Fannie Mae. Borrowed Funds Secured by an Asset
The arithmetic is unforgiving. Say you earn $8,000 per month gross and currently carry $1,200 in monthly debt (existing mortgage, car loan, credit card minimums). That’s 15% DTI before housing. Add a $300 interest-only HELOC payment and a projected $2,100 new mortgage payment including taxes and insurance, and your total obligations hit $3,600. DTI jumps to 45%. Under manual underwriting that leaves almost no room for error, and under automated approval it burns most of the buffer.
The practical effect: a HELOC-funded down payment reduces how much house the lender will let you buy. Every dollar of HELOC payment eats into the mortgage payment you can carry.
Risks That Outlast Closing
Three features of HELOCs can go sideways after you’ve already committed to the new mortgage.
The Draw-Period Cliff
Most HELOCs give you about ten years of draw period with interest-only payments, then convert to a repayment phase of 10 to 20 years at full amortization. The payment jump can be severe. A $50,000 balance at 9% runs about $375 per month interest-only; shift to 20-year repayment and the payment rises to roughly $450. At 11%, repayment-phase payments climb to about $516. Borrowers who stretched to qualify for the new mortgage get that increase at the worst possible time.
Freezes and Reductions
Federal regulations let the HELOC lender freeze your line or cut the limit when your home’s value drops significantly below the appraised value used at origination, when the lender reasonably believes you can’t meet repayment obligations due to a material change in your finances, or when you default on a material term. “Significant decline” is defined as the initial equity cushion between your credit limit and the appraised value dropping by 50% or more. If your home was appraised at $400,000 with a $300,000 mortgage and a $60,000 HELOC limit, the cushion above the HELOC is $40,000. A $20,000 decline in home value cuts that in half and can trigger a freeze.4Consumer Financial Protection Bureau. 12 CFR 1026.40 – Requirements for Home Equity Plans
If the market turns between opening the HELOC and drawing on it, you could find the line frozen right when you need the funds for closing. The lender must reinstate the credit once the triggering condition goes away, but that doesn’t help if your purchase contract has a closing deadline.
Variable Rates With Lender-Set Caps
Almost all HELOCs are variable, usually tied to prime. Federal law requires a lifetime maximum rate in every HELOC agreement but doesn’t set that ceiling; the lender does.4Consumer Financial Protection Bureau. 12 CFR 1026.40 – Requirements for Home Equity Plans A common structure is a cap five percentage points above your initial rate. Open at 8.5% and your rate could reach 13.5%. On a $60,000 balance, that’s the difference between $425 and $675 in monthly interest alone. When you’re carrying this debt alongside a new mortgage, rate increases hit twice as hard because you’ve already maximized your debt capacity to qualify.
Before committing, check your HELOC’s lifetime cap and calculate the worst-case monthly payment. If you can’t absorb the maximum rate alongside the new mortgage, the plan is too fragile to execute.
Tax Treatment of the Interest
Most borrowers assume HELOC interest is deductible. It usually isn’t when you’re using the funds for a down payment on a different property.
The One Big Beautiful Bill Act, enacted in 2025, made the Tax Cuts and Jobs Act’s mortgage interest provisions permanent. Interest on a HELOC is deductible only when the borrowed funds are used to buy, build, or substantially improve the home that secures the loan. Using a HELOC on your primary residence to fund a down payment on another property does not qualify.5Internal Revenue Service. Real Estate Taxes, Mortgage Interest, Points, Other Property Expenses Before 2018, up to $100,000 of home equity debt was deductible regardless of use; that provision was suspended by the TCJA and is now gone for good. The acquisition debt deduction remains capped at $750,000 across your primary residence and one second home, counting first mortgages plus any HELOC used to improve the securing property.6Internal Revenue Service. Publication 936 (2025), Home Mortgage Interest Deduction
There is one meaningful exception. If the HELOC proceeds go toward buying a rental property, IRS interest tracing rules let you categorize the interest by how the money was actually used rather than by what secures the loan. Interest allocable to producing rental income gets reported on Schedule E and offsets rental income. Interest allocable to other investment property goes on Schedule A as investment interest, deductible only up to your net investment income for the year.6Internal Revenue Service. Publication 936 (2025), Home Mortgage Interest Deduction
If you split a HELOC between a home renovation and a down payment elsewhere, you have to track every dollar and allocate the interest proportionally. Your lender will send Form 1098 reporting total interest paid, but determining how much is deductible, and under which category, is on you.7Internal Revenue Service. Other Deduction Questions
When the Strategy Actually Works
This approach fits a narrow profile: substantial equity in your current home, strong income relative to your total debt load, and a credible plan for paying the HELOC down within a few years. Real estate investors buying rental properties often use it because the rental income helps service the HELOC and the interest may be deductible against that rental income.
It falls apart when borrowers are stretching to qualify. If the HELOC payment pushes your DTI near the lender’s ceiling, you’ve built a structure with no margin. A job loss, a rate increase, or a frozen credit line can cascade into trouble on both properties at once. Borrowers in that position are usually better off waiting and saving a cash down payment, because the cost of carrying two leveraged properties on razor-thin margins almost always exceeds the cost of patience.