One of the most common mistakes in fix-and-flip investing is underestimating the rehab budget. Overspending on a renovation — or missing a major cost category entirely — can turn a promising deal into a losing one. Here's how to build a rehab budget that holds up.
Start with a Scope of Work
Before assigning dollar amounts, walk the property and document every item that needs to be addressed. A thorough scope of work covers both cosmetic updates and mechanical systems.
Typical categories include:
- Kitchen: Cabinets, countertops, appliances, sink, fixtures
- Bathrooms: Tile, vanity, toilet, shower, plumbing fixtures
- Flooring: Refinish hardwood, replace carpet, install LVP or tile
- Roof: Age, condition, any visible damage or missing shingles
- HVAC: Age of the system, whether it heats and cools properly, ductwork condition
- Electrical: Panel capacity, outlet and switch condition, any knob-and-tube or aluminum wiring
- Plumbing: Supply line material (copper vs. galvanized), drain line condition, water heater age
- Windows and doors: Broken seals, single-pane glass, damaged frames, security
- Paint: Interior and exterior, including prep work for peeling or damaged surfaces
- Landscaping: First impressions matter for buyers — curb appeal drives offers
- Foundation and structure: Any visible cracks, settling, or water intrusion signs
- Permits and inspections: Required permits vary by jurisdiction; always budget for them
Missing a category — especially a mechanical one — is how flippers get surprised. Walk every inch of the property, including the attic, crawl space, and electrical panel.
Get Real Numbers, Not Guesses
Rule-of-thumb per-square-foot estimates can get you in the ballpark, but they're not a substitute for actual bids. Before committing to a deal, get at least two contractor estimates for the major scopes: roof, HVAC, and anything structural. Cosmetic work is easier to estimate yourself.
Be honest about what you're getting into. A full gut renovation (down to studs) costs dramatically more than a cosmetic flip. Permits, engineering reports, and structural work add time and money that many investors overlook.
Add a Contingency Buffer
Even well-underwritten rehabs encounter surprises. Once the walls come down, you find what wasn't visible on the walkthrough: old pipes, mold, substandard prior work. Budget a 10–20% contingency on top of your base estimate. For older properties or extensive scopes, lean toward 20%.
If you don't use the contingency, it becomes profit. If you need it, you're covered.
Factor In Contractor Overhead
If you're working with a general contractor rather than managing subcontractors yourself, expect to pay 10–20% overhead on top of the raw labor and material costs. GCs coordinate schedules, manage subs, and take on liability — that's what the margin covers. Include it in your budget from the start.
The 70% Rule as a Sanity Check
Once you have a rehab estimate, use the 70% rule to quickly check whether the deal makes sense at your target purchase price:
Maximum Allowable Offer (MAO) = (ARV × 70%) − Rehab Costs
The 30% buffer is meant to cover holding costs, closing costs (buying and selling), and your profit margin. If the seller's asking price is above your MAO, you either need to negotiate down or pass on the deal.
For example: if ARV is $300,000 and estimated rehab is $50,000:
MAO = ($300,000 × 70%) − $50,000
MAO = $210,000 − $50,000 = $160,000
If the property is listed at $185,000, the deal doesn't work at current numbers — unless you can negotiate the price down or reduce the rehab scope.
What ARV Means and How to Estimate It
ARV (After Repair Value) is the estimated market value of the property after all renovations are complete. Getting ARV right is just as important as getting the rehab budget right — overestimating ARV is as dangerous as underestimating costs.
To estimate ARV, look at recent sales of similar properties (comparable sales, or "comps") in the same neighborhood that are already in updated, move-in-ready condition. Use the same square footage range, bed/bath count, and lot size. Comps more than 6 months old or more than a mile away carry less weight.
Use the Calculators Together
The Rehab Budget Calculator helps you build a line-item estimate across all major categories, including contractor overhead. Once you have your total rehab cost, plug it into the 70% Rule Calculator to calculate your maximum allowable offer and estimated profit margin.