1. Budgeting from a single quote. Without a local partner running comparisons, owners abroad often accept the first bid they receive — and it's the only one they have any real basis to judge as fair or high.
2. Assuming "doesn't need a permit" is true. Contractors are financially motivated to start quickly, and permit requirements slow that down. Verifying independently — rather than accepting a verbal assurance — is the difference between a smooth renovation and a legal problem later.
3. Underestimating older-building surprises. Outdated electrical systems, structural walls in unexpected places, and plumbing that needs full replacement rather than cosmetic work are the norm in older Jerusalem apartments, not the exception. Quotes based on a surface-level walkthrough routinely miss these.
4. Not building leverage into the contract before work starts. Once demolition begins, a change order can't easily be shopped around for a second quote — and pricing tends to reflect that. Owners who negotiate payment phases and contract terms upfront keep real leverage if something goes wrong.
5. Trusting the contractor to confirm their own work. The person who did the work has an obvious conflict of interest in judging whether it was done correctly. Skipping independent verification is the single most common reason owners discover problems only at the final walkthrough — when it's expensive to fix.
The fix for all five is broadly the same: verification, competitive bidding, and contract terms decided before work starts, not during it.