Non-owner wants survey
Walking a line and digging up pins can get you a criminal trespass charge here. I suspect many would be surprised if they did a little research.
Right of entry in Idaho and Oregon puts the landowner and surveyor closer to equal footing than most. Being both things I am OK with that.
As others have said, the big issues are access and payment.
I've done this for a prospective buyer, and the seller didn't have any problem with me being there, since it was to facilitate the sale.
I'd just make sure that you get at least half up front in case the sale goes sour. That happens, and your client obviously no longer has any interest in the survey results, or paying you to finish.
I had a client who hired me after an offer subject to survey. He offered 10k per acre for 43 acres. The survey showed 39. Never seen anyone so happy to pay for survey. (they were using [by mistake??]a deed that had 4 acres cut out after it was recorded ). My client is a sharp tack and had a suspicion.
I had the last house I bought surveyed due to encroaching garage and lots lines.
I'll never buy any properties ever again unless a real honest to God survey is performed.
It's pennies on the dollar for a transaction that is usually the biggest financial thing most people will ever experience.
If a seller wouldn't let me get a survey I wouldn't even bother and back out under the contract with that sole reason.
Something to hide is no thing to buy.
I recently did a survey where an adjoiner owned a portion of the parent tract and was hostile to the purchaser of the remainder. She refused access to the northeast corner of the parent tract. I contacted her adjoiner to the east and got permission to cross their pasture to shoot the corner. If that gets you before the board in Idaho or Oregon, then I'd suggest they have way too much time on their hands.