i never refuse payment in advance of the report but do not require it. I issue the report in a locked draft format by email that may be read but not printed. No bank or insurance company will accept a report in this format
(like the survey sample reports on my website).
This serves two purposes, one - it proves i have done the work and now deserve payment. Two - it gives me a chance to make corrections (yes ! I do occasionally make mistakes) and provide more detail if an issue is not understood.
I have done insurance surveys for people who don't want to pay me when they find they cannot get insurance due to problems i have discovered and reported on..... It's my fault they can't insure an unsafe boat !
On occasion i have found it hard to collect on pre-purchase surveys because i found enough issues that the buyer walks and decides he shouldn't have to pay because he did not buy the boat (twisted logic).
over the years i have taken about 12 people to small claims court to get paid. Curiously (or not ) all but one was a lawyer. If i find out my client is a lawyer, this is the only time i want cash up front, no cheques thank you