Buying 2nd hand has *mostly* been okay for me. A couple of duds along the way, but for the most part, it's been alright.
I guess these days I'm more inclined to go with a seller on Ebay that is either a company and offering a return period, or the goods have been serviced (and ca' canny with that - I'm not convinced many of these services are anything more than a wipe down with a duster - so check what the element of service was), or they're a long standing audio independent seller (i.e., not a business) and feedback is excellent.
My current stereo has a 35 year old Kenwood DP990- SG as my main player, bought a couple of years ago from a charity in Manchester that specialised in refurbishing electronics, my speakers (AVI ADM 9RSS actives) were bought from 2ndhandhifi and I think they were NOS. Cambridge 752BD was new ten years ago, Cambridge Alva ST & DACMagic 200M were "opened box" from Cambridge in 2023, but really absolutely mint. Wharfedale SW150 subwoofer was new just the other day, so everything is a bit of a mix.
My spend on used gear these days is limited to around £100-150 for a CD player. That'll get you some really nice old Sony models, a brand I rate very highly - they turned out some terrific gear and well worth a look. Much of their ES range is hopelessly overpriced, although some of the lower end of that range is coming into more realistic pricing.
I used to have the Sony CDP-911E which was a fantastic purchase - I think I got it for around £75? It lasted just over a year (or at least, I wasn't going to pay any more to have it fixed, so it went to recycling). Then I picked up the Kenwood.
Shop around, be patient, wise up on the gear you're interested in, and remember what Tony Bennett once said - "buy right, buy once".