You have the following categories of hamfest sellers:
1. High priced, works perfectly, they know it and they want top dollar for it.
2. Works more or less, may have minor issues, generally they are electro-mechanical problems. (price variable, depending on time, mood, etc...)
3. Works perfectly, they want to get rid of it ASAP and will take reasonable or unreasonable offers for it.
4. Complete garbage, they know it, you know it, they still want top dollar for it, you run, not walk away from it.
5. Not working 100%, but not terrible, they know it, you know it, they are honest, you make a deal for gear with issues and its a win-win (my favorite)
6. Lying POS, "It works fine" - Does not work or works with major issues. - May you burn in hell.
7. Has no clue what they are selling. (Can be good or bad)
8. Thinks it has problems and does not - A somewhat rare occurrence, but does happen with some frequency. I've paid next to nothing for
gear that the seller swore was broken (on very rare occasions highly technically competent hams, inexplicable). Well, it works.
9. Honest estate sellers. "Was my great uncle Elmo's stuff". Price and quality varies widely.
10. Broken, looks fairly good, cheap, seller seems to be okay..... Ugh... My nemesis... Tens of thousands spent....
11. Works, cheap, clean, good deal. (oh yeah!)
12. Variations and combinations of the above.
Of course you can buy new, I can go to HRO today and buy a Collins 75S-3C... Not...
Some hams don't want new gear all the time. Me personally, I've never bought a new radio ever.
Don't purchase used if you can not fix it, unless it is so cheap that it does not matter.
Your mileage may vary.