Hello Netforce,
Let me just give you a general guide.
Camera Condition:
General/Cosmetics, this somewhat personal preference. If you don't mind a little scratch here and there (expected for old cameras).
Minor functional, look out for cracked viewfinders, inaccurate meters, cracked knobs, worn out/degraded light seals and mirror foam , ect. (light seals and mirror can diy fix( if you dare, quite messy)
Major functional, meter not working, inaccurate shutter speeds, mirror mechanism damaged, missing knobs, ect. (This might cripple the camera for your use, so price must chop chop chop or don't buy)
Note: CLA a camera locally can be costly and really not worth it for some cameras.
Prices:
Local shops, local shops tend to be quite expensive compared to others (can't blame them as they got to earn some income, pay rent, raise families, ect) but more safe IMO as got short warranty ect. Generally not worth IMO unless you are looking for something specific, have loads of money and are too lazy to look for alternative.
Local BnS, lower than shops but can be erratic (different people, different price for same condition). Just do a search and judge by pass prices and gauge for yourself. You can arrange a meeting and see and touch all you like to look for defects before payment!
Online, online shops like KEH or ebay. Do a search compare prices. Ebay can be really cheap and worth it but also risky as it is overseas and item conditions are hard to judge, when there are problems they can be difficult and takes ages to resolve.