Carrying Costs on a Flip: What Borrowers Consistently Undercount

We reviewed a batch of declined or restructured bridge scenarios from Q1 and Q2 2026, and the same problem kept surfacing: borrowers had modeled their interest carry at six months and stopped there. No transfer tax line. No utility hold. No buffer for a market where the average Cook County suburban flip now sits on the market 38 days before closing — up from 27 days just two years ago. That 11-day swing alone, on a $450,000 exit price financed at 11.5%, adds roughly $1,500 in interest carry that nobody budgeted for. Multiply that across every cost category and you see why deals that looked like $40,000 profit plays are closing at $12,000 or less.

Interest Carry Is the Starting Point, Not the Full Picture

Private bridge and hard money rates in the Chicago metro are running 10.5% to 12.5% as of Q2 2026. On a $300,000 loan, a 12-month carry at 11.5% costs $34,500 in interest alone. Most borrowers do that math. The problem is they do it at six months and assume a clean exit — no delays in permitting, no contractor gaps, no soft market.

Our desk prices scenarios assuming the realistic hold period, not the optimistic one. If a project is in a suburb where DOM has drifted past 35 days, we're stress-testing to at least eight months. That adds one to two months of interest carry the borrower hasn't modeled. On a $280,000 draw balance, two extra months at 11% is roughly $5,100 that evaporates from the projected spread.

The fix is mechanical: run your interest carry at your realistic construction timeline plus 60 days for listing, negotiation, and closing. If your market's DOM is trending up — and in Cook County suburbs it is — add another two to four weeks on top.

Cook County Transfer Taxes Are Not Optional Line Items

Illinois imposes a state real estate transfer tax, and Cook County layers its own graduated structure on top. On a $450,000 sale price, the seller-side transfer tax exposure clears $2,800 before you factor in any municipal stamps. Chicago proper adds its own city transfer tax, which is among the highest of any municipality in the state. If your exit property sits inside Chicago city limits, you are looking at a combined seller-side exposure that can run $6,000 to $9,000 depending on the transaction structure.

We see this omitted from pro formas constantly. Borrowers account for broker commissions — usually 5% to 6% — and they account for closing costs in a general sense, but the transfer tax line either gets buried inside a vague 'closing costs' bucket or it disappears entirely. On a deal with a $35,000 projected gross profit, a $3,000 tax hit you didn't model is an 8.5% reduction in your margin before you've paid your lender back.

Utilities, Insurance, and Taxes: The $8,000–$14,000 Nobody Budgets

On a six-month Chicago-area rehab, utilities, property insurance, and prorated property taxes collectively run $8,000 to $14,000 depending on the size of the property. That range comes from projects our desk has funded across Cook and DuPage counties over the past 18 months. A 1,400-square-foot brick bungalow in Berwyn sits at the lower end. A 2,800-square-foot two-flat in Logan Square or a larger single-family in Elmhurst pushes toward the top.

Builder's risk and vacancy insurance is the line that surprises people most. Standard homeowner's policies don't cover vacant properties under active renovation. A vacancy and rehabilitation policy on a $400,000 ARV property runs $150 to $250 per month — call it $1,200 to $1,500 for a six-month hold. Miss that and you're either uninsured during construction or paying out of pocket for a policy you didn't price into the deal.

Property taxes are prorated at closing, which means the seller — your entity — credits the buyer for the portion of the tax year you held the property. In Cook County, where assessed values and tax rates vary dramatically by township, this proration can run $2,000 to $5,000 on a mid-range asset. It shows up on the settlement statement as a deduction from your proceeds. It is not a surprise if you modeled it. It is a gut punch if you didn't.

• Builder's risk / vacancy insurance — $150–$250/month; required for any lender draw; standard homeowner's policies are void on vacant rehab properties.
• Prorated property taxes — Credited to buyer at closing; in Cook County this runs $2,000–$5,000 on most SFR flips and comes directly off your net proceeds.
• Utilities during rehab — Gas, electric, and water average $200–$400/month for an active job site; many borrowers assume zero because the property is vacant.

Extended DOM Is the New Underwriting Variable

Cook County suburban flips averaged 38 days on market in Q2 2026. That is not a crisis number, but it is a meaningful shift from the 27-day average we saw in Q2 2024. What it means practically is that the assumption of a 30-day sale window — which is what a lot of pro formas still use because it was accurate two years ago — is now costing borrowers an extra eight to ten days of carry on every deal.

Eight days of interest on a $320,000 balance at 11.5% is about $810. That is not a large number in isolation. Pair it with $2,800 in transfer taxes you didn't model, $1,400 in insurance you didn't price, and a $3,200 property tax proration, and you have erased $8,200 in margin from a deal that was already priced tightly.

Our underwriting now uses 45 days as a base DOM assumption for Cook County suburban assets when the borrower hasn't provided recent comp velocity data. For properties in price tiers above $550,000, we push that to 60 days. If a borrower can show us active listings and pending data that justifies a shorter window, we'll adjust. But the default has moved, and pro formas that haven't moved with it are going to keep producing outcomes that don't match projections.

Building a Carrying Cost Model That Holds Up

The carrying cost line on a flip pro forma should be a discrete, itemized section — not a percentage plug. We've seen borrowers use 2% of ARV as a catch-all carry estimate. On a $475,000 ARV project, that's $9,500. Sounds reasonable until you add up actual interest ($18,000–$24,000 for a six-to-eight-month hold at current rates), transfer taxes ($2,800+), insurance ($1,200–$1,500), utilities ($1,200–$2,400), and property tax proration ($2,500–$4,000). You're at $26,000 to $34,000 before you've paid closing costs on the acquisition side.

The model we walk borrowers through at Matrix starts with the loan balance and runs a monthly interest figure. Then it adds a fixed line for insurance, a utility estimate based on property size, a transfer tax calculation based on the projected exit price and municipality, and a property tax proration based on the current assessed value and local mill rate. The total gets stress-tested at the base hold period and again at base plus 60 days. If the deal still works at the extended scenario, it's a deal worth funding.

• Interest carry — Calculate at your realistic construction timeline plus 60 days; stress-test at an additional 60 days given current Cook County DOM trends.
• Transfer taxes — Run the actual county and municipal calculation at your projected exit price — don't bury this in a generic closing cost percentage.
• Insurance and utilities — Budget $350–$650/month combined for a standard SFR; vacancy policies are non-negotiable for any lender-funded project.
• Property tax proration — Pull the current Cook County tax bill, divide by 12, multiply by your projected hold period in months — this number belongs on the pro forma.

Where We See Borrowers Get This Right

Recurring clients who've done five or more deals with our desk tend to carry a running cost log from closed projects. They know their actual utility spend per month because they've tracked it. They know what their township's property tax proration looked like at closing. They've been hit by a transfer tax line once and they never miss it again. That institutional memory is worth real money — it's the difference between a 14% gross margin and a 9% one on a project where the ARV estimate was accurate to begin with.

First-time or early-stage flippers don't have that history yet. Our suggestion is to pull the HUD-1 or closing disclosure from every deal you've closed and build a line-item average. Three closed deals gives you a reasonable baseline. If you haven't closed three yet, ask your title company for a seller's net sheet with every line populated — they can run this before you're under contract. It takes 20 minutes and it tells you exactly what's coming off the top at exit.

"The pro forma that breaks even on paper breaks the bank when DOM runs 11 days longer than you modeled and the transfer tax line is blank."

Bottom line

Accurate carrying cost modeling — interest at realistic hold periods, transfer taxes by municipality, insurance and utility hold costs, and property tax proration — is what separates a deal that pencils from one that breaks even or worse. With bridge rates in the 10.5–12.5% range and Cook County suburban DOM at 38 days and rising, the margin for modeling error has narrowed. A project that produces $38,000 gross profit at a 27-day sale assumption produces $21,000 at a 45-day assumption once you cascade all the carry variables. That is not a rounding error.

If you have a flip scenario in the pipeline and want to run the carry model before you commit to the purchase, submit it to our desk. We'll price the debt and walk through the cost stack with you — no charge for the conversation, no obligation to close with us. That's how we've structured every borrower relationship since we started funding in this market.