Possible purchase, looking for pointers

Hi, new around here. Decided to make a post and ask for some sage advice. Going later this week to look at a 78 Southwind 18 with a 351W. Price seems a tad low, but boat isn't what you'd call the "best kept" and most stellar example ever. Owner says nothing wrong with it, water ready, with the exception of some water in the oil. The seats are a bit faded and carpet could be better. But from pics it looks overall solid.
When asked more detail on the engine, the oil level is not high, just milkshaked. Claims it was his late family member's boat, and he discovered the shake while test running it to get ready for sale. Said he ran while hooked to garden hose and it fires right up and runs and idles fine. I have been around cars my whole life, so a bit of milkshake doesn't really scare me too much for the price. Figure I'll start with fresh oil change and see what comes of it.
Any advice there would be appreciated, but my main question is for guidance on the "what to look fors" on these guys. Most of my experience has been with bass boats and pontoons. This is a low cost adventure and feeler for what these boats are really like to live with overall. Won't break my bank to say goodbye if need be.

Any advice is appreciated in advance!

I think I would ask the seller to change the oil and filter, run it a bit and then see.....

67 ski nat wrote: Try to find and buy the nicest boat you can afford happier later Do not buy just because it’s there I typically assume milkshake means new or Rebiuld engine Do you need and enjoy mechanical projects. Channeling my inner grandpa Good luck if you get it. Pictures

Thanks everyone for the input. The owner kept acting oddly and rescheduled a couple times, constantly left me on "read" when I would ask which lake to meet at for a float test. Finally I decided to tell them I would pass, the wife and I decided it was a better idea to get a boat from a local marina. We budgeted and decided we would just make a large down payment on a used boat from them.
Bit more than we initially wanted to spend, but the boat is local since new, one owner, and has been housed indoor at the marina over winter every year with records. We went and did a ride along test and the marina is being nice enough to offer us (slightly) discounted storage and winterization for being customers for as long as we own the boat, as well as a small warranty for the next month against any large undisclosed issues.
Unfortunately for this forum, it isn't a Correct Craft, but a Rinker Captiva 216. 67 hours on the clock. Like new shape. Very well kept, all original covers included, no fades or cracks. Figure I'd rather make a small monthly payment for a couple years to have a much better condition boat I can actually use without TOO much worry.