Boats of that age should be relatively inexpensive so as long as nothing seems punky, and the price is right, then go for it. My personal, biased and technically unfounded opinion would be the 4 Winns. I am not a fan of Bay Liner or Sting Ray. I have no opinion on the Glastron. Also I had a Volvo Penta on my 91 Renken and had nothing but trouble with the Shift that came with it. I agree on having the survey done... though a $500 survey for a $500 dollar boat may be a tad excessive!
So, there you have it! I have always bought old boats and they were fine for a long time.
IG