Is it not the commercial custom that an estimate of repairs, made by the person who will do the repairs, is in fact an offer to make the repairs, which the other party may reject or accept? The estimate, is really a “bid” (or in common parlance, a “free estimate”). If in fact the person is acting as a consultant, then wouldn’t the consultancy fee have to be arranged in advance?
Either halacha or American law will look to the local custom. In my experience, estimates are offers to repair at a certain price, not consultations generating a fee.