Why It Matters
Under a cost-plus contract, your contractor bills you for every receipt and every labor hour, then adds their profit margin on top — typically 10 to 20 percent. You gain full visibility into where your money goes. You lose the safety net of a guaranteed total. Use it when scope is genuinely uncertain; avoid it when the work is straightforward and predictable.
At a Glance
- Contractor markup: typically 10 to 20 percent on combined materials and labor
- Opposite structure: fixed-price (lump-sum) contract
- Best use case: complex rehabs with uncertain or evolving scope
- Transparency feature: investor sees all receipts and time logs
- Main risk: no cost ceiling unless you negotiate a Guaranteed Maximum Price
- Hybrid option: cost-plus with a GMP cap to limit exposure
How It Works
The contractor tracks every dollar spent on materials — lumber, fixtures, subcontractor invoices — and every hour of labor. At the end of each billing cycle, typically weekly or biweekly, they submit an itemized invoice. You pay those actual costs plus the agreed markup.
If the markup is a percentage, say 15 percent, and a given week costs $10,000 in materials and labor, your bill is $11,500. If the markup is a fixed fee, say $8,000 for the entire project, that fee gets distributed across draws regardless of how costs fluctuate week to week.
The defining feature is transparency. You can audit every line item. You know exactly what your contractor paid for tile versus what they charged for labor. That visibility is valuable when rehab costs are hard to estimate upfront — structural repairs, foundation work, old homes with surprises inside the walls.
The trade-off is exposure. Because you absorb all cost increases, a discovery of rotted floor joists or outdated electrical panels becomes your problem immediately. There is no contractor absorbing that risk on your behalf.
One important variant is the cost-plus with a Guaranteed Maximum Price, sometimes called a GMP. Here the contractor agrees to absorb any overruns beyond a specified ceiling. You still get the transparency of cost-plus billing, but your downside is capped. In exchange, contractors typically negotiate a higher fixed markup or a share of savings if the project comes in under the GMP.
Real-World Example
Priya found a 1940s bungalow with good bones but unknown plumbing and electrical conditions. The contractor she trusted refused to give a fixed price without opening walls first. They agreed on a cost-plus structure at 15 percent markup with a $90,000 GMP.
Actual costs came in at $78,000 — $12,000 under the cap. The contractor kept the savings because they had negotiated that term upfront. Priya paid $89,700 all in (materials plus labor plus markup on actuals). She would have preferred to pay less, but the GMP protected her from a scenario where hidden problems pushed costs to $120,000. She reviewed every invoice, confirmed the work matched the bills, and closed knowing her cash-on-cash return stayed within projections.
Without the GMP, the same job could have run wide open. Full cost-plus without a cap is a trust-based arrangement — appropriate only with contractors you have worked with before.
Pros & Cons
- Full transparency into material and labor costs — you see every receipt
- Contractor has no incentive to cut corners to protect a fixed-price margin
- Accommodates scope changes without contentious renegotiation
- Works well for discovery rehabs where hidden conditions are likely
- Aligns contractor incentives with doing the job correctly, not cheaply
- No cost ceiling unless a GMP is negotiated separately
- Requires active oversight — you must review invoices, not just approve draws
- Budget can balloon if scope expands or materials costs rise
- Harder to compare bids across contractors (no single apples-to-apples number)
- Creates more administrative work tracking receipts and time logs
Watch Out
Markup inflation is the most common abuse. Some contractors bill materials at retail then apply the markup percentage on top — effectively double-charging. Negotiate that the markup applies to contractor cost, not retail price, and require receipts to verify.
Time padding is the second risk. Without fixed-price accountability, labor hours can stretch. Set clear milestones and check in regularly. An idle crew on your dime is a real scenario.
Also watch your property-tax timeline. Long, open-ended rehabs can trigger reassessments or extend your holding period, both of which compress your NOI projections once the property is stabilized.
Finally, always define in the contract what counts as an allowable cost. Travel time, tool rental, financing charges on materials — these are gray areas that become disputes without written clarity.
Ask an Investor
The Takeaway
A cost-plus contract trades price certainty for scope flexibility and transparency. It is the right tool for complex rehabs in older properties where scope is genuinely unknowable before work begins. Pair it with a GMP to protect your downside, require receipts on every invoice, and only use it with contractors you trust. For cosmetic rehabs or jobs with a clear scope of work, a fixed-price contract is almost always the better choice.