Do I need insurance before I'm even under contract on anything?

I asked an insurance broker this while I was setting up, before I had anything under contract. The answer I got was that general liability is the piece that covers you for third-party injury and property damage during site visits, and it's usually written per-occurrence with a small annual premium at low limits. She was clear that the contractor should be carrying his own coverage and I should ask for his certificate, because if he's uninsured the exposure lands somewhere and it might land on me. Specifics differ by carrier and state, so she wanted to look at my actual activity before quoting anything.

@bramble that matches what I put in my startup cost sheet. What I still can't figure out is whether E and O type coverage applies to someone who isn't licensed, since a lot of the errors risk in assigning is about what you told the seller. Asking my attorney next month.