Buying Used Gear

You can save loads of money and get used gear, but unless you can hear & test it first there is a lot of risk involved. Better still, if you can (or aren't scared of trying to) repair and solder you could save thousands buying equipment in need of some TLC. 

As with cars (and records!) you're going to be looking for careful owners: equipment that is still in the original boxes with the packaging material and manuals etc would indicate that the current owner has taken good care of the kit. If you browse sites like the subreddit R/budgetaudiophile for long enough you'll get an idea of the sort of basic setups and brands that people gravitate towards.

Standard things like if the seller is reputable, if the original gear is built to last, and any testing the seller claims to have done will also add to the picture.