Used bikes can be great values if they don't need much work done, or if the selling price is so low it's worth spending the money to rebuild or replace key components.

All the bikes I've owned since resuming cycling a couple of years ago were purchased used. With each purchase I've learned more and know what to look for and which mistakes to avoid. None of the bikes needed any serious work and I was able to do most of it myself, re-acquiring tools I'd sold off years ago when I thought I'd never ride again, and absorbing as many tutorials as I could digest online.

The main suggestion I'd make, which is often omitted from many DIY bike evaluation/inspection tutorials -- remove the wheels. Ask the seller first, of course, but it's usually okay, especially with convenient quick releases. Spin the axle between your fingertips and feel for any grit, resistance or unevenness.

I don't mean hold the axle and spin the entire wheel -- the momentum will mask any minor hub problems. Same as spinning the wheel on the bike. These techniques will only reveal serious problems that cannot be repaired cost effectively -- completely worn out hubs with bad bearings and no grease.

But by holding the wheel steady off the bike and spinning just the axle, like dialing a combination on a padlock, you can feel for problems that indicate the hub needs servicing but may be okay for now. It should feel snug, without any discernible sideways play, but should spin smoothly with a buttery feel and some smooth resistance from the grease. If it spins too freely the bearings may be dry or using only oil rather than grease. Usually grease is preferred to resist contamination by water and road grit.

Use the same technique to check the bearings in the bottom bracket -- where the cranks are attached -- and headset by turning the handlebars and fork. Again, checking the headset may be easier with the front wheel detached, since the weight and momentum of the wheel may mask minor problems.

Check the frame tubes and joints for cracks. Minor dents may be okay with steel and aluminum frames but I'd skip any dented tube and keep looking.

Check the forks. Sometimes a crashed bike may have forks bent inward. An owner or mechanic might have attempted to straighten the forks but I wouldn't trust that kind of damage. Even if the forks and headset were replaced, there may still be damage to the top tube and downtube.

Check the chain stay -- the bottom, rear tubing running parallel with the ground. Some kickstands clamp directly to the chain stay tubes and can dent or even crush those tubes. Other kickstands -- like on my Univega hybrid that came from Germany -- are cleverly designed to clamp around the tubing without denting or crushing. The best kickstands bolt to a plate welded between the chain stay tubes and seat tube, provided specifically for attaching kickstands, especially double leg kickstands. But I've seen these only on some work bikes and Euro-styled bikes. My Globe Carmel has such a plate for attaching a kickstand, but the bike itself was provided with a single leg unstable chainstay crusher that I removed immediately. I plan to replace it with a double leg stand that attaches to that plate.

It can help to find a reputable reseller. Besides buying used from a local bike shop, some cities have experienced mechanics who work from their home shops, flipping bikes. Check their customer feedback, or ask around your area for recommendations. I found several local Facebook groups that have been great for those recommendations. And as a bonus I've made some great friends with whom I enjoy riding.