In the NW, to moor a boat, sail or power, these days you
have to have insurance. Insurers normally require a survey to assess their risk before they will issue a policy.
So you might as well start out with a good survey.
That's after you have done as much pre-purchase inspection as you can reasonably do on your own.
We have never had to turn down a potential purchase based on a survey, but some friends of ours did. They were out the cost of the survey, but they felt that it had revealed too many problems that they did not want to address.
Note B: a good surveyor will want you to observe them, give you commentary and info as they do their work, and will provide a document that will not only assess the condition of the boat but will map out the repairs/upgrades needed in the near future.
Note C: I would contact several potential insurers that you have in mind and just ask them what they need to see and know before writting you a policy. Sometimes getting an objective opinion really helps you focus.
Sidebar: true story that may or may not be of any help: When we were buying our prior boat from a seller up in BC Canada, we needed to find a local surveyor we could trust. We live in Portland, OR, had no clue on who to rely on.
After some thought, I called three of the larger banks in Vancouver BC, and spoke to their loan officer(s). I asked who
they would trust to survey a boat before they would risk their bank's money on a potential loan.
After a chuckle or two they each gave me a short list and I picked an excellent guy that overlapped a couple of lists! They all said that they liked my logic.
Best of luck,
Loren