I sold a nice 79 440 Invader a couple years ago for $700. I would describe it as a real nice rider, it wasn't perfect, but was mechanically sound, ready to ride with studs and carbides. You might be able to make a few bucks fixing it up and reselling it. But if it's been sitting for 6 years, it'll likely need lots of work to get it running properly (crank seals, fuel lines, carbs cleaned, recoil rope, freeing up suspension shafts, slides, ski wear bars, etc.). It's not a bad deal if you're looking for a project sled for yourself, or if this one is in immaculate condition, but I wouldn't suggest buying it to flip. Good luck!