Estimating rehab costs by property age & condition

Rehab is the single input most likely to sink a tax-deed deal, because it's the number you control least before you own the property. The goal isn't a perfect estimate — it's a defensible one that leaves room for the surprises that always come with distressed inventory.

Start with a per-square-foot baseline

BidWise anchors rehab to square footage and the age of the structure, because older buildings hide more expensive problems (knob-and-tube wiring, galvanized plumbing, no insulation). A reasonable starting grid for tax-deed properties, which tend to be more neglected than a typical MLS flip:

| Structure age | Baseline rehab | | --- | --- | | Newer / recently updated | ~$35 / sq ft | | Mid-age (roughly 1980–2005) | ~$55 / sq ft | | Older (pre-1980) | ~$85 / sq ft |

These are starting numbers for a full cosmetic-plus-systems refresh. They already run higher than a standard retail flip because tax-deed homes are often vacant, vandalized, or deferred for years.

Condition flags that move the number up

Adjust upward when you see:

• Roof age or visible damage — a full replacement is often $8k–$20k+.
• Foundation movement — cracks, sloping floors, sticking doors. This is the one that turns a deal into a money pit; budget conservatively or walk.
• Water intrusion or mold — staining, musty smell in photos/descriptions.
• Missing systems — stripped copper, no HVAC, gutted kitchens.
• Long vacancy — the longer it sat, the more you'll find.

What can move it down

• Recent permitted work (roof, HVAC, electrical) on file with the county.
• Solid brick or block exterior with intact windows.
• A livable interior that needs cosmetics, not systems.

Build in a contingency

Whatever number you land on, add a contingency — 10–20% is sensible for tax-deed work — before it flows into your max bid. The most common modeling mistake is treating a clean baseline estimate as a ceiling. On distressed property it's closer to a floor.

Rule of thumb: if you can't inspect the interior, assume the worst plausible version of what the exterior and photos suggest, and price accordingly.