[st_za]

This is the headline shopping info that I sent a friend recently to help sift through the cheaper end of the JK pool too:

JK = 2 door
JKU/Unlimited = 4 door
Parts and ads commonly just get labelled with the "JK" series code.

Spec:
Sport = Dana 44 rear diff, smaller Dana 30 front diff, 3.73 diff ratios and 2.72 low range transfer case ratio.
Overland = Same running gear as the Sport but with body coloured fenders and hardtop as well as leather seats.
Rubicon = Dana 44 front & rear diff, 4.10 diff ratios, front & rear E-lockers, 4.10 transfer case and electronically disconnectable swaybar.
The 2007 Sport used 4.10 gears too.
There have been a few non-Rubicon special editions with factory rear lockers or LSDs too but these owners tend to know what they have and price them higher.

Interior:
The 2007-2011 models' interior is very simple with no steering controls and very flat seats.
2012+ seats are a bit better but the rest of the interior is much more modern and generally better quality.
Most 2012+ models have steering wheel controls. It's a major pain to retrofit if it doesn't have them.

Soft tops:
The 2010+ soft tops are better designed and more durable and the 2012+ tops are a slight bit better again.
A lot of people never use their soft top so they sell it separately.
They're generally very durable but they're cheap on FB Marketplace if you need a replacement.
If it is included but they have never used it, check that it has the tailgate bar and plastic brackets, door surrounds and roll bar mount brackets.

Engine:
The 2007-2012 models used the thirsty and underpowered but reliable 3.8 v6.
The 2012-2018 models used the still relatively thirsty but decently powerful 3.6 v6 that is proving to be dependable.
I don't have experience with the 2.8 diesel but the few people who I know run them, love them.
A few 2012-2013 3.6 had relatively minor issues that should mostly be sorted out by now.

Gearbox:
The 4 speed auto in the 2007-2011 3.8 is just OK.
The Mercedes-built W5A580 5 speed auto in the 2012+ petrol's and diesels is durable, reliable and smooth.
The 6 speed manual that came in all years is easy to shift and relatively reliable.

Having experience with a 2010 manual 3.8 Sport 2 door and now a 2015 auto 3.6 Sport Unlimited with all the mods, I think it's worth saving up and keeping an eye out for a 2012+ auto 3.6 Unlimited. The engine, gearbox and interior is worth the extra money in my opinion.

A 3.8 manual Rubicon is an interesting alternative in your price range, especially because the bigger front diff, 4.10 ratios and lockers pay for themselves if you want to do rock crawling or you want to run 35s. As with all vehicles, only a test drive will tell you if a manual, a 3.8 or the older interior is worth the money saved to you.

Good luck with your search. This damned Covid-tax and state border closures makes car-buying way more difficult than before.