Wayne Nash gives a few pointers on what to look for when you go used rig shopping.
First consider the actual size rig you will need. Make an honest appraisal of the depth and size of the holes you typically drill, and match the rig to the job. I know a driller who bought a rig about tw o sizes too big for his work; he wanted it for the occasional big job. Guess what? In addition to a bigger rig, he got bigger payments and a lot of locations he can't fit into. And while his competitor is going to the next job, he's either winching out o r filling ruts. Bottom line: less bottom line.