Used diesel trucks are insane. Even if youre buying from owner a good half ton/3/4 ton diesel truck goes for 18k+. And in talking late 90's early 2000's.
And trust me you are going to want a used car. anything older than anything 2012 is malware spy device, and they all have shitty computers in then and start locking down parts of it you can actually repair. You'll start having to bring the car in so you can pay 2 grand for something that uses to be a 50 dollar fix and a trip to pick and pull.