If buying a used LR4, IMO the CPO warranty is the way to go. Read the warranty presented to you, but it should provide coverage for 6 years from the first sale date or 100,000 miles, whichever comes first. The LR4 has less issues than the LR3 but some are still there. You will need lots of suspension parts at around 75K miles including tie rods, ball joints, bushings and maybe wheel bearings. These are normal wear & tear items on this heavy vehicle that will be covered by a CPO warranty. Another common V8 LR4 issue is a minor water pump leak that is really expensive to fix and will be covered under a CPO warranty.
As for being a 2013 model, that is good. That was the last year of the V8. When it came time to replace our LR3, I didn't like the 2015 LR4 compared to the 2013 LR4 already in our garage. Not a fan of the V6, start-stop, running boards, etc. I had to find a CPO 2013 and am glad I did.