Hello!
If your child sits/lays comfortably in an Xplory seat unit, it's no wonder you're thinking about getting a Crusi. You can click the same seat unit on the chassis - plus the frame design will, with all probability, suit your husband much more. As a more classic shape, the Crusi frame is more stable and stronger. But I have to warn you - if you think the Trailz is too robust for you, Crusi may also seem quite big. It's quite similar to Trailz in terms of chassis size, of course with the lighter foam wheels. The option of attaching an additional, second seat unit at the bottom part also means the chassis must be designed as a bigger one, able to perform all the "heavy-duty" features. Count on it being larger - and quite high - before folding, but also space-occupying even after folding. Moreover, a weight of over 27 lbs (12.4 kg) is not the lowest, so you need to be prepared for this.
If you're ok with that, however, I think - especially for just one child - it would be a very good choice. In winter, thanks to the thick, large wheels (even though made out of foam), you'll certainly be ok in almost any strolling situation - I would not be worried there.
And what to look for when choosing a second-hand one? I would, ideally, went to see the offered stroller for real (not just from the pictures). Even if it's a hand-down, it will not be a cheap thing. Check if it is not too rattly if there's not too much give in the joints... Of course, look closely if you won't find any rust or other serious damage (but these would be deal-breakers, of course). Creaking of the chassis would, actually, not be that much of a problem - that you can resolve by proper lubrication with WD-40 in the wheel joints, and silicone spray in the other - plastic - ones. It should all be fine afterward. Also, check the wheel joints (remove them if you try the stroller out before buying, if you can) and generally check their condition. The foam is ok to be looking a bit used, that's normal. And position it and put it together if everything is as it should be. Otherwise, I would not be too worried - besides serious damage that may happen (but should be quite visible), this brand is quite nice in terms of quality of used materials and designs, and it should be ok if you don't notice anything obvious.