>>1796574anyway, as for just general advise on buying a used bike
(good luck finding anything helpful out of the free association mental vomit that is topnigger)
wheels and cranks are the most expensive things that typically wear out.
(if rim brake) you want to check the brake track on the rim isn't badly concave, or with any major dings in it.
Spin the wheel and watch the brake pads. A little bit out of round is easy to fix but if there's a bad wobble it might be toast. Or if there are any really loose or broken spokes. Rust on spokes is fine.
Likewise, when you spin the wheel, if it's really rough, the bearings are probably toast. You can service it but likely it will never roll that well.
Having a good (expensive, and good condition) set of tires on a bike is also a major selling point, but it's often better to pay less for a bike with shot tires, and then have your pick upgrading, than to have the price of tires that aren't that suitable for you included with the bike.
Check the chainrings aren't shark toothed or missing teeth. Look up some pictures of this to see what it means. Chainrings/cranks can be quite expensive, and when they are badly damaged it means the entire drivetrain is shot.
The other major thing to look for is frame/fork damage. On steel bikes a front end crash shunting the fork blades back is common. They should curve forward from the line of the headtube, if they come back, don't buy the bike. On an aluminium or carbon bike, scour all over the frame for hairline cracks. Some rust is fine.
