specific to O'Day 27, not sure, but . . .
Get the owner to take you out for a sea trial. If you like it, haul it out and get a reliable surveyor to check it out.If you cant do the surveyor, you will have to find the problems yourself. If you can do the surveyor, he can point things out that you would have overlooked. In any event, expect to pay much more than you are thinking now to fix what could be broken.Some of my thoughts,Seriously consider replacing the standing rigging now or the standing rigging and the mast later.Expect problems with the head--even if it is just stinky.Look closely at the wiring, fuses, everything, and see whether there is any corrosion, cracks, fires. Do they all work? Running wiring is a pain and the wire isn't cheap. What electronics do you need, etc. Minimum IMO is depthsounder and radio.Read up on blisters and fiberglass hulls. There are several schools of thought floating around. I don't know which one is "right," but it does good to know what others are thinking about. Read up a lot on blisters. This boat will probably have them and you need to learn how to identify them (from outside and from looking at the inside of the hull) and decide whether this 27 is the one you really want. Did I say read up a lot on blisters? Yeah, I thought so.Buy Epoxy by the gallon and look for fiberglass on ebay.You getting lifejackets and cushions?Speaking of cushions, boat cusions are expensive so if they are missing, well . . .It may not apply to you, but I would recommend that you look for a boat that is in good shape with all the pieces instead of buying a boat and having to refit it with new hardware, even if you have to drive a long way to get it.