Former rental is something to consider but it wouldnt disqualify a vehicle for me. How does the price stack up against Carmax, Kelley Bluebook, etc? If its a screaming deal and you've looked it over well, I'd still consider it. I'd skip the warranty. Those things are priced to make the warranty company money not you. Not worth the paper they are written on. If money is tight with the baby on the way, paying cash for something that will get you by beats a car payment any day.
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2006 2500HD, RCLB, 4X4
6.0, 4L80e, 14 bolt