Yep, there are 2 types that get into K98s, those that do their homework beforehand and those that don't. I'll admit, I got burned for my own stupidity, maybe it was the Adderall and energy drinks mixed with some MAAAAAD DOG. You are lucky, your lesson was $400, mine was much more. If you want to get into Mausers, stick around read posts, and ask questions. You can place a WTB ad in the marketplace, but I'd kinda hang out for a bit because there is a lot going on in the world of collecting K98s.
Pics aren't clear. But Looks like some extreme moisture damage. Could have been in a basement, after which someone possibly tried to weld the corrosion--who knows? Wheeled, said screw it, and tried to cover it up via a poor re-bluing job. No way this was turned on a lathe like the seller says.