Home Builder Profit Margins: Why Specs Burn Cash in a Slump

A home builder profit margin in the real world lands closer to 10-12% net than the 30% rule of thumb the industry quotes. That gap — and the question of who is carrying the construction loan while you earn it — is what separates builders who survive a soft market from builders sitting on finished specs they can’t move.

Jay London has built over 1,000 homes across Oklahoma and developed roughly $50 million in commercial projects over the last five years. He’s also gone broke twice. What follows is his accounting of what residential and commercial construction actually net, why he ran 100% custom for three years before pivoting, and the structural decisions that left him with zero spec inventory while his builder friends are stuck.

This is a guide to margin math, debt placement, custom sales cycles, and the parts of a build business an owner should never hand off.

From the Real Estate Pros Show

This article draws on an interview with Jay London of Jay London Homes on the Real Estate Pros Show, hosted by Quentin Edmonds.

What a Home Builder Actually Nets Per House

The rule of thumb in home building is 30%. Almost nobody hits it. After 25 years and more than a thousand homes, Jay London puts the realistic net at 10-12% once everything is said and done.

That number matters because it changes how much cushion a builder has when a job goes sideways. At 12% net, a single trade overrun, a four-month carry extension, or an appraisal that comes in light can erase the entire profit on a house. At 30% — the number builders tell each other at conferences — you’d have room to absorb two or three of those. You don’t.

London is blunt about the social media version of this business. “I see these guys, I made $100,000. No, you didn’t. I know what you paid for it. I know what you did.” In a market where everybody in the trade knows roughly what lumber, labor, and lots cost, the published per-house profit numbers are mostly theater.

Commercial looks more lucrative, and in dollar terms it is — but mostly because the zeros are bigger. The percentage band is not dramatically different. London’s working frame: if you’re operating somewhere between 10% and 25-30% in construction, you’re doing well. There are businesses knocking out 60%, 70%, even 100% margins. Construction is not one of them, and building a plan around the assumption that it might be is how builders end up over-leveraged on the way into a slowdown.

The practical implication: if your margin is structurally capped near 12%, your competitive edge can’t come from squeezing a few more points out of a build. It has to come from how the business is financed.

Who Carries the Construction Debt Changes Everything

This is the decision that determines whether a slow market costs you a year or costs you the business. On a spec, the builder holds the construction loan and eats the carry until a buyer shows up. On a custom, the homeowner holds the note and the builder is essentially a general contractor working someone else’s money.

For three years before pivoting into commercial, London’s shop ran 100% custom. “It wasn’t our money. We was basically GC’ing projects for customers that needed their homes built. Customs are difficult, but you have no debt with customs. The customer carries the debt.”

The result is visible right now. He describes a lot of builder friends sitting on specs they can’t move in a bad new-construction market. He has none — partly from the commercial pivot two years ago, but mostly from the three years before that spent deliberately running a no-builder-debt model.

Frame this as a risk decision, not a style preference. Specs are faster to sell when the market is hot because the buyer doesn’t have to wait 18 months. They also concentrate every dollar of timing risk on your balance sheet. Customs are slower, more administratively painful, and involve dealing with a client’s selections for a year and a half — but your downside in a frozen market is a thinner pipeline, not interest payments on unsold inventory.

If you want to run specs, the honest version of that decision is: how many months of carry on how many houses can the business absorb before it breaks? Answer that before you pull the next construction draw, not after.

Customs are difficult, but you have no debt with customs. The customer carries the debt. I’ve got a lot of builder friends sitting on specs. Fortunately, I don’t have any.

— Jay London, Jay London Homes

The Custom Home Sales Cycle Builders Underestimate

A custom home client is a two-year relationship, and most builders price and market as if it’s a two-month one.

London’s breakdown of the timeline:

• Roughly six months with a prospect before you convert them into a signed contract
• About 18 months building the house
• Then the warranty period on top of that

“They’re a customer for two years before you don’t hear from them again.”

That length changes the arithmetic on everything. Conversion rate becomes a lagging indicator — leads generated this quarter won’t show up as contracts until two quarters out, and won’t show up as revenue for two years. A builder who turns marketing off in a slow month doesn’t feel it for six months, and a builder who turns it back on doesn’t feel that for six months either. You are always steering a vehicle with a long delay between the wheel and the tires.

It also changes what a lead is worth and how many you can handle. London rates his marketing a 5 out of 10 and is deliberately cautious about spending more. His reasoning when asked whether he’d invest $1,500-2,000 a month in marketing was not about cost — it was about capacity. “We get back to the point: how much work do I want?”

That’s a legitimate position for a custom builder with a limited project-manager bench. If every converted lead commits you to 24 months of involvement, lead volume beyond your delivery capacity isn’t growth. It’s a liability with a deposit attached.

Why Overcommitting Is the Contractor’s Real Nightmare

The reputational damage that kills contractors usually isn’t bad workmanship. It’s unfinished work.

London’s description of the trap is precise: “In the construction world, you take on everything that comes at you because you don’t know when it’s going to stop coming at you. And then we start committing to more than we can handle, and then we start getting the bad publicity from not getting the stuff done.”

That’s the mechanism. Feast-or-famine fear drives a builder to say yes to every job in the pipeline. The jobs all start. None of them finish on time because the same project manager, the same framing crew, and the same owner are spread across all of them. “Not that he does bad work — he just don’t get crap done.” Twelve months later the builder has a full schedule, poor cash conversion, and a reputation problem he can’t explain to prospects.

The defense is uncomfortable because it means turning down revenue. London’s current posture is to grow the rental and portfolio side rather than chase gross revenue on the build side: “Instead of looking good on paper with assets, I want to look good on paper on cash flow.”

For a builder deciding whether to take the next job, the useful test isn’t whether the margin pencils. It’s whether you have the delivery capacity to finish it inside the promised window while finishing everything already under contract. Gross revenue you can’t deliver on costs you future deals.

Banking Relationships Are the One Thing You Don’t Delegate

Asked what he’d never hand off, London didn’t say sales or estimating. He said the money.

“I would never delegate dealing with the bankers and where I get the money, because that is my superpower. My bankers loan to me. They don’t loan to the company.”

He works with five bankers, has a close personal relationship with each, and borrows millions of dollars a year to operate. That’s the key detail for any builder reading this: in a capital-intensive construction business, the lending relationship isn’t a vendor arrangement that an operations hire can manage. It’s underwritten on the owner personally — his track record, his reputation, and twenty-plus years of showing those specific people that he finishes what he starts.

You cannot transfer that to an employee by giving them a title and a contact list. London built those relationships from the ground up and treats them as the asset they are.

The same logic applies to the books. His wife came out of corporate accounting and has run the financials for all the companies for more than twenty years. He calls her the biggest control freak on the financial side, which in this context is a compliment — the person who sees every dollar move through the business is the person who knows what the bankers are going to see before they see it.

For a builder scaling a team: delegate the field, delegate scheduling, delegate selections and procurement. Keep the lender conversations and keep real visibility into the numbers. Those two are what let you keep borrowing when the market tightens.

Scaling Slowly After a Go-Big-or-Go-Home Decision Backfires

The business decision London says he’d take back is the “go big or go home” mindset he brought into commercial development.

He entered expecting millions. He had built self-storage, industrial, flex bays, and apartment complexes, and developed roughly $50 million in commercial across five years. Then the economy turned. Two projects, he says, “sucked the life out of me” over two years of physical and mental grind. He’s down about $6 million in unrealized equity across a few projects and has commercial buildings sitting stagnant. Gross revenue fell from the $7-8 million range to $2-3 million.

His correction has four parts, and they’re worth taking literally:

1. Do what you’re actually good at. He’s pivoting back to custom home building — the thing he did for 22 years — because “regardless of how bad the economy is, somebody always wants to build a home.”
2. Scale slowly. “You don’t have to be a millionaire tomorrow. But you can be a decamillionaire in five.”
3. Build portfolio assets that cover their own debt. He’s focused on small multifamily — duplexes and fourplexes — not to make a lot of money on them, but to hold assets that service their debt and appreciate.
4. Stop doing $25-an-hour work. Growing up on a farm, he knows how to do everything, so instead of making calls to find someone, he does it himself. He names this as a direct cause of the last two years: “That’s a downfall for somebody in my position.”

The pattern underneath all four: diversify income streams so one bad vertical doesn’t take the business down. It took two trips to broke for that lesson to stick. “You need it coming from everywhere, because when this gets bad, this can still be paying the bills.”

Frequently asked questions

What is a realistic net profit margin on building a custom home?

Around 10-12% net after everything is said and done, according to Jay London, who has built over 1,000 homes across 22 years. The 30% figure often quoted as the industry rule of thumb is rarely what a builder actually keeps.

Across construction generally — residential or commercial — anywhere in the 10% to 25-30% band is considered strong performance. Businesses outside construction that run 60-100% margins are not a useful comparison.

Why do builders with spec inventory get hurt worse in a downturn?

Because on a spec, the builder holds the construction debt and pays the carry every month until a buyer closes. When new construction sales slow, that cost keeps running against a 10-12% margin that was never designed to absorb many extra months of interest.

On a custom build, the homeowner carries the loan and the builder functions as the GC. The builder’s downside in a frozen market is a thinner pipeline rather than payments on unsold houses.

How long does a custom home client relationship actually last from first contact to end of warranty?

About two years. London’s breakdown is roughly six months working a prospect before converting them to a signed contract, then approximately 18 months building the home, plus the warranty period after completion.

That timeline means conversion rate is a lagging metric and that lead volume needs to be matched to delivery capacity, not maximized.

Should a residential builder diversify into commercial development?

Diversifying income streams is sound — London’s own hard-won advice after going broke twice is that you need revenue coming from multiple directions so one bad vertical doesn’t sink the business. But the entry posture matters more than the decision itself.

The decision he says he’d take back is the “go big or go home” mindset he brought into commercial, which contributed to roughly $6 million in lost unrealized equity and two projects that consumed two years. His corrective is to do what you’re good at and scale it slowly rather than betting the business on a fast entry into a new asset class.

What parts of a home building business should the owner never hand off?

The banking relationships and real visibility into the financials. London works with five bankers who lend to him personally rather than to the company, built over decades, and borrows millions a year to operate — he considers handing that to an employee unworkable.

Nearly everything else can and should be delegated. He identifies his own control-freak habit of doing $25-an-hour field work himself, rather than making calls to get it covered, as a genuine drag on the business.

The bottom line

Before the next project starts, write down who holds the construction note on every house and commercial building currently in your pipeline, and calculate how many months of carry the business could absorb if none of them sold. If that number is uncomfortable, shift the mix toward work where the customer carries the debt — that single structural change does more for survivability than any margin improvement you’ll find in the budget.