If your not a mechanic. Don't pretend to be one.
Do two things:
1) Run a Carfax. Before even leaving your driveway. Some repairs and maintenance can be left off. But it will tell you how many and where each owner was, any accidents, most repairs and maintenance and how often its been done, if its been totaled, if it has odometer fraud. And many other things. For $30-$40 its worth every penny. First call the person and ask about all of the above. You'll find out real quick from the Carfax whether you can trust them or not. And if they won't give you a plate or vin to run one - run the other way.
2) Pay for a professional inspection. "Would you mind if I paid for an inspection at a local mechanic?". Or hire a mobile mechanic off of Craigslist or similar. To go with you. This will cost around $200. But again, well worth the money. And don't bother with this step until you've seen a clean Carfax.
Have them at least run codes and have a list of items you want looked at. They may have a list. But make a list anyway. Make a list for yourself too. For when your looking at it and when you're driving it. Have the mechanic drive it too.
I have lost close to two grand before for little things like turn signals, emergency lights and other small things. But you want to operate every single thing on the Jeep and confirm it works. Including the 4x4. Also drive it on surface streets and the highway - at speed.
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Between those two steps (and looking it over and driving it yourself) I have uncovered dozens of vehicles that would have been a real problem. While shopping for myself, wife, son, sisters, mother etc.
The Carfax has revolutionized how one looks for a used car. The days of guessing and trying to "read" if a seller is truthful are over. Often times every single little mom and pop place they ever had it worked on will show up on a Carfax. It is full of essential information.
And what isn't uncovered in a Carfax will show up on a legitimate inspection. It will also give you ammunition to negotiate with. Whatever repairs may be needed can be taken off the top. Depending on how fair the asking price is.
If you can afford it try to find a one or two owner car with no negative records on the Carfax. That was regularly serviced. If it doesn't come up on the Carfax ask for receipts. Any well kept car will have an owner that keeps receipts.
Lastly, try to never buy from a used car lot. You're just paying an extra middleman fee. And their job literally is to rip you off. Lawyers and used car salesmen - I'd take advice from my worst enemy before I trusted them. And there is a reason bluebook shows a higher price for dealer price than private party.
You want a one owner car. From some retired, anal retentive, military guy, with OCD. Who is overly paranoid about maintenance. Lmao!

Good luck!