Need Tips On Buying Used Tractor

Hi,
The first thread on this forum is a whole list on the questions a driver may ask the company. I found that information very helpfull to me and Im sure to many other. I was hoping someone with good knowledge about tractors can do the same with this thread but with purchasing used tractors. For example, what to look for ( mechanical, not hp, speed etc..), is it functioning well and so forth. Your response and knowledge would be well appreciated.

Thanks