If you can afford it, go with Landice, lifetime warranty on EVERYTHING and 1 year labor & structurally own all
. Just make sure you list any beneficiaries that may get the treadmill later on in life so the warranty title transfers over to them when you register it. If you can't afford Landice, go with True (built like tanks). Life Fitness makes a really good treadmill to (T5 and up series, very comfortable to run on) but their warranty is only so-so. If you can't afford either of the three, then go with Vision, they make a pretty good treadmill at their price point.
Stay far away from the crap at department stores like Academy, it's cheap for a reason!!!
Remember, you get no warranty when you go used, so if you don't know how to fix treadmills, good luck on finding somebody that'll repair it when needed, it's not cheap just fyi (think parts and labor at this point).
Hope that helps, let me know if you need some more info