If you are a member of BoatUS they use to have a list of surveyors for members and a service called value check to give you the "Blue Book" value. Nadaguides is also useful to get a value. It will cost you nothing to survey the boat if you use the man in the mirror, a check list and call around for some estimates to fix issues you encounter and adjust your offer accordingly.
I made my own survey checklist and used it when I was looking at houseboats a few years ago and modified it for a runabout to write up a report on Chris Craft I was asked to survey. It is very easy to check for waves in the skin of a hull with a laser level these days and if there are waves there is probably an underlying structural problem you should run away from. The following is the houseboat version of my survey form. Also measure the beam and check it with the design data, if a boat was lifted in a sling it creates and inward crushing force at the sheers and can bend ribs if the adhesive and fastners are corroded or missing. Also scrape some paint samples from a few areas into plastic ziplocks and get them tested for lead, a steel boat made in the 50s could have a lot of red lead paint and you should run from that too as it can be expensive to abate. Forensic Analytical in Hayward charged me $75 a sample to measure lead in paint last year from a Chris Craft, you can get test kits at the hardware store for a faster cheaper result.
Name Notes Adjust
Hull identification number
CF
asking
length x beam
year
bow integrity
chine integrity
frames integrity
stern integrity
transom integrity
deck integrity/level
side planking
short block conversion
transmission
motor start/idle/run
motor hours
rudder integrity
steering function
cooling jacket
upholstery
12v fuse block/batteries
navigation lights
risky/costly/slow=1
safe/cheap/fast=7
BoatUS value check
Tools to bring for survey: mirror, rubber mallet, hammer, pen clip board
laser level, paint scraper, envelopes, camera, flashlight, putty knife, sand paper, tape measure