How to Estimate Rehab Costs Before You Make an Offer

Ask any experienced investor how they lost money on a flip or a BRRRR, and you'll hear some version of the same story: the rehab ran over. The purchase price is fixed on the day you close. The repair budget is a guess until the walls are open. The better that guess is, the safer the deal.

Here's a practical way to estimate repairs before you make an offer, and how to use that number to decide what you can afford to pay.

Step 1: Walk the property by system, not by room

It's tempting to walk through a house room by room and react to what you see: dated kitchen, ugly carpet, stained ceiling. The expensive surprises usually hide in the systems, so walk it in this order and take notes on each:

1. Roof: age, visible wear, soft spots, signs of leaks inside.
2. Foundation and structure: cracks, sloping floors, doors that stick.
3. HVAC: age of the unit and ductwork condition.
4. Plumbing: pipe material, water heater age, any signs of leaks.
5. Electrical: panel age and capacity, outdated wiring.
6. Exterior: siding, windows, drainage, grading.
7. Interior finishes: kitchen, baths, flooring, paint, fixtures.

The first five items are where budgets get blown. Cosmetic work is predictable. A failed sewer line is not.

Step 2: Price each line item

For each item, write down what needs to be done and a cost. Early on, get real bids from contractors in your market, even on houses you don't buy. Over time, you'll build your own price list for things like cost per square foot of LVP flooring, a full interior repaint or a standard bathroom refresh, and you'll be able to estimate quickly and accurately.

Don't forget the costs that aren't "repairs" but still come out of your pocket: permits, dumpsters, cleaning, and utilities during the work.

Step 3: Add a contingency

Every rehab has surprises. Add 10% to 15% on top of your estimate for a light cosmetic job and 15% to 20% or more for an older home or a heavy rehab. If you don't end up using it, that's profit. If you skip it and need it, it's a loss.

Step 4: Count your holding costs

Every month the property sits under construction, you're paying for the loan, taxes, insurance and utilities. A three-month rehab that turns into six can quietly eat thousands of dollars. Estimate your timeline honestly and multiply it by your monthly carrying cost.

Step 5: Work backward to your maximum offer

A common starting point for flips is the 70% rule:

Maximum offer = (After-repair value × 70%) − repair costs

Example: If the after-repair value (ARV) is $300,000 and your repair estimate including contingency is $45,000:

$300,000 × 0.70 = $210,000
$210,000 − $45,000 = $165,000 maximum offer

The 30% gap is meant to cover closing costs on both ends, holding costs, agent commissions and your profit. It's a screening tool, not a law. In expensive markets or on rentals you plan to hold, you may adjust it, but the discipline of working backward from the ARV keeps you from falling in love with a house and overpaying.

Step 6: Track actuals against the budget

Once the work starts, log every expense against its line item. You'll catch overruns early, while you still have time to adjust scope, and you'll build the real-world cost data that makes your next estimate better.

The bottom line

You make your money when you buy, and you can only buy right if you know what the repairs will cost. Walk the systems first, price every line, add a contingency, count your holding costs and let the numbers set your offer. Use the Investor Deal Analysis Workbook to organize your deal assumptions and the Job Cost vs. Estimate Profit Tracker to compare actual project costs with your budget.

This article is for educational purposes only. Repair costs vary widely by market, property and contractor. Always get professional inspections and contractor bids before committing to a purchase.