Depends....from a true professional if it is just a general consult with no potential business for years...I would say $300-$500. If core samples are taken probably more.

However if you are really close to building and the guy knows you are not a "tire-kicker" and about to pull the trigger then it might be free or your money refunded once the project begins.

We recently had a retention pond of sorts built by the same guy that built our main pond before we bought the property. He came out, walked the property, did some measuring and looking thru some tri-pod instrument, gave his advice, told us about what it would cost and that was it. No charge for the consult because he knew we were ready to go. So we called him a week or two later and said "lets do it". He couldn't start for 2-3 months because he was so busy...but it worked out great.

Fishing has never been about the fish....