How to Estimate Rehab Costs for a Flip: Line-by-Line Budget and Contingency

Rehab budgets are where many first flips go wrong. The purchase price is fixed at closing, but the renovation cost can grow every week if the scope was vague or a major system was missed. A disciplined, line-by-line estimate protects your profit and makes your 70 percent rule calculation meaningful. Here is how experienced flippers build one.

All unit costs are illustrative as of 2026. They vary widely by region and contractor; verify with at least two local bids per major trade.

Step 1: Set the scope from the comps

The right renovation is the one that matches your comparable sales, not your personal taste. Look at photos of the renovated homes that sold at your target ARV and match their finishes.

Over-improving is one of the most common ways flippers turn a profitable deal into a break-even one.

Step 2: Walk the property with a checklist

Bring a flashlight, moisture meter, ladder, tape measure and camera. Check:

• ☐ Roof age and condition, flashing, gutters, signs of leaks in the attic
• ☐ Foundation cracks, sloping floors, water in the basement or crawl space
• ☐ HVAC age and function
• ☐ Water heater age
• ☐ Electrical panel type and capacity, visible wiring problems
• ☐ Plumbing material, leaks, water pressure
• ☐ Sewer line condition (a camera inspection is cheap insurance on older homes)
• ☐ Windows and doors
• ☐ Kitchen and bath condition
• ☐ Flooring by room and square footage
• ☐ Exterior siding, paint and drainage
• ☐ Signs of pests or termite damage
• ☐ Potential lead paint in pre-1978 homes, and possible asbestos in some older materials

Photograph everything and measure each room. Bring a contractor on the walkthrough if you can.

Step 3: Build a line-item budget

Step 4: Add the right contingency

Contingency is not optional padding. It is the money for the surprises you cannot see until walls are open: rotted subfloor under a toilet, knob-and-tube wiring behind plaster, a cracked sewer line.

Step 5: Compare the full budget with your quick estimate

Many investors start with a rough rehab number to screen a deal. In this example, a rough $45,000 estimate turned into about $66,600 when every line was priced. Rerun the 70 percent rule with the real number:

• ARV $300,000 × 70% = $210,000
• Minus rehab $66,585 = maximum offer about $143,400

Using the rough $45,000, the maximum offer would have been $165,000. Paying that price with a $66,600 rehab would cut your profit by more than $21,000. This is why the line-item budget must come before a firm offer.

Step 6: Get bids and lock scope

For each major trade (roof, HVAC, electrical, plumbing, flooring, kitchen), get at least two written bids with the same scope. Compare line by line. Then write a scope of work for your contractor that specifies:

• Exact materials and finishes, with model numbers where possible
• Quantities and locations
• Who buys which materials
• Permits and inspections
• Schedule and draw milestones
• Cleanup and disposal

Vague scopes lead to change orders, and change orders are where budgets break.

Step 7: Track actual versus budget weekly

Weekly tracking lets you make trade-offs early, such as a simpler backsplash to offset a roof overage, rather than discovering the problem at the end.

Build your own unit cost database

After each flip, record what every line actually cost, with the date, contractor and quantity. Within a few projects, you will have your own local unit costs for roofing per square, flooring per square foot installed, interior paint per square foot, bath refreshes and kitchen packages. Your own numbers are far more reliable than national averages or online calculators, and they let you estimate a new property in an hour instead of waiting days for bids.

Cost per square foot: useful, but limited

Some investors use a rough rehab cost per square foot for light, medium and heavy rehabs to screen deals quickly. That can sort listings, but it fails badly when a home needs a roof, HVAC, sewer line or foundation work. Use it to decide which properties deserve a walkthrough, never to set your offer.

Common mistakes

1. No contingency, or one too small for an older home.
2. Missing big-ticket systems: roof, HVAC, sewer, foundation, electrical panel.
3. Over-improving beyond the comps.
4. Vague contractor scopes.
5. Forgetting permits, dumpsters and cleaning, which add up quickly.
6. Ignoring lead-safe requirements on pre-1978 homes.

Questions readers ask

How accurate should a rehab estimate be before I make an offer?

Accurate enough that your contingency covers realistic surprises. For most flips, that means a line-item budget built from a walkthrough, with the big systems (roof, HVAC, electrical, plumbing, sewer and foundation) priced by a contractor or from your own recent costs. If you cannot get inside the property before making an offer, use a larger contingency and include an inspection contingency in your contract where possible.

Should I use a general contractor or hire trades directly?

A general contractor costs more because they add overhead and profit, but they coordinate trades, schedules and permits. Hiring trades directly can save money if you have the time and experience to manage sequencing, inspections and quality. Many first-time flippers use a general contractor for the first one or two projects, learn how the work is sequenced, and then manage trades themselves on simpler cosmetic flips.

How do I estimate holding costs during the rehab?

Multiply the expected months from purchase to sale closing by your monthly costs: loan interest, property taxes, insurance, utilities, HOA dues, lawn care and security. Add a month or two of buffer, because permit delays, contractor scheduling and slow sales extend timelines more often than they shorten them.

Do I need permits for cosmetic work?

Paint, flooring and cabinet replacement often do not need permits, but electrical, plumbing, HVAC, structural changes, roofing in many areas and some window replacements usually do. Unpermitted work can delay a sale when the buyer's inspector or appraiser finds it. Check with your local building department and budget permit fees and inspection time.

Your next step

Take one property you are considering, walk it with the checklist above, and build a full line-item budget before you make an offer.

The full guide, House Flipping for Beginners, includes the rehab budget template, contractor scope and agreement guidance, financing comparisons, ARV and deal analysis worksheets, and a step-by-step plan for your first flip, for $0.99.