no truss rod supro with bowed neck?

Honestly, I'd have to say there's really no way of knowing from that description. Could be a candidate for fret dress and setup, could need a refret, could be much less or much more. It's all in the details and degree, which really can't be judged until it's inspected.

 

So long as it is a relatively smooth, consistent area of relief or backbow, you should be alright. Even a more sudden kink may not be too big of a deal if it's minor to modest, and fairly even on both sides. Those things can often be taken care of with compression fretting and leveling. What you' ll have to be concerned with is any twists or kinks being modest to severe, or noticably inconsistent from treble to bass sides. That's where it can get more difficult to correct, and repair methods greatly vary depending on the direction and severity of the problem.

The trickiest part is trusting the seller's eye. It seems they're trying their best to be honest. Still, I see so many instruments that were described as something like "minor relief" by someone then when I look down the neck literally jump and have to do a double take it's so warped. Then again, there are plenty of folks who do know what they're looking at, and they may be spot on with their description.

If it's nearby and you'd be going to pick it up, you'll just have to trust your own eye in evaluating it. If it's something you would be having shipped as a final no-returns sale, then it may be a risk. If you think it's selling for a price where if the neck bow did turn out to be too serious you could resell it (with problems honestly listed) for a similar price, then I'd say go for it. If you're paying closer to the market price for a maintained, fully functional and playable instrument, I don't know it I would buy it without an approval period

 

use it for slide in open tunings

 

Great point. I had one customer who ended up with a similar instrument with a bad neck, and he had be machine a custom base for a Hipshot Trliogy to match the old tailpiece footprint/mounting holes. Turned out to be a very cool guitar.