There are 2 good books on surveying. One is on Amazon, The other is Don Casey's book. Search for it, I'm sure you'll find it.
Whether you pay for a survey or not, you should know what to look for before, during and after purchase. Surveyors are human and can miss things. I would suggest you study up, do your own survey and then definately hire a surveyor to verify your findings. Much better than just writing a check and not knowing what you are paying for.