The rehab number is where flips and BRRRR deals are won or lost. Overshoot your budget and a promising deal turns into a break-even slog; underestimate it and you might not be able to refinance out. You don't need a contractor's precision to make a buy decision, but you do need a disciplined estimate — and a healthy contingency.
Start with a scope, not a guess
Walk the property (or the photos) room by room and write down what actually needs to change: roof, HVAC, electrical, plumbing, kitchen, baths, flooring, paint, windows, and exterior. A number pulled from thin air is worthless; a number built from a list of real line items can be checked and corrected. The big-ticket systems — roof, HVAC, foundation, electrical — are what turn a cosmetic refresh into a gut job, so price those first.
Where investors blow the budget
- Ignoring the systems they can't see — old wiring, failing sewer lines, and foundation issues rarely show up in listing photos.
- Pricing off the cheapest possible finishes, then upgrading mid-project.
- Forgetting soft costs: permits, dumpsters, utilities during the hold, and holding costs while the work drags on.
- Assuming the timeline. Every extra month of holding is more interest, insurance, and taxes with no income coming in.
Add a contingency — always
Even experienced flippers add a contingency of roughly 10–20% on top of their scoped budget, because something always surfaces once the walls are open. Treat that buffer as spent until proven otherwise. If a deal only works when the rehab comes in perfectly on budget, it doesn't really work.
Feed it into the deal, not a napkin
Once you have a scoped estimate plus contingency, run it through the actual numbers: purchase, rehab, ARV, and selling costs for a flip; or the post-rehab rent and refinance for a hold. That's the only way to know whether your renovation budget still leaves a profit — and it's exactly what the flip profit calculator is for.