I'm not familiar with the specifics of that machine, but my advice (for any new equipment, really) would be:
- Firstly, make sure the machine will work with whatever production software you use- or, at least, that any required software is relatively easy to use. Learning new software is a hug time suck (even though it's sometimes the only option).
- No matter what the manufacturer might say, it's not really a router table. I'm not saying it won't cut, but it is absolutely not a machine you want to make channel letters or thick, dimensional aluminum items with. If that's not what you're planning on using it for, no biggie- but it's a consideration.
- Ask to see a demonstration of the machine cutting materials you'd use it for, and provide your own file(s) so you can determine whether the items were cut correctly.
- Inspect the machine top to bottom.
- Check rails for degradation (nicks/gouges/rust- but hopefully they'd be stainless). If there are gears/toothed rails, make sure all teeth are good (none missing).
- Look for wear/nicks/etc. on the belt. I've never seen any equipment that uses a belt not have a crazy high price to replace said belt.
- Cosmetic damage, though not usually a big deal, can indicate poor maintenance, so make sure to check everything. If you think you did, I'd suggest checking again.
- Ask how many hours are on the spindle (they may or may not know). Most machines have a good life for those things, but they do wear out.
Kongsberg, from what I've heard, is a quality machine, but read everything you can find online about the one you're looking at- particularly reviews (good and bad), because that's a big investment (even used) to have buyer's remorse about.