Any guidelines on eBay purchases?

[Siegfried]

Exceptions prove the rule, as we say in German...

I just bought a HP45 advertised as "probably not working" which turned out to be fine (except for the batteries).

I'd say my results for "not working" are about 50/50 but as said it depends a lot on whether the seller is likely to be able to test it or just found some old stuff when clearing out granddad's study.