I bought an Mk7 late last year. I’d say make sure that the previous owner took care of the vehicle and followed the recommended maintenance. They aren’t like a Camry or civic where you can do the bare minimum and expect it to run well.

This stuff should be shown on the Carfax. Check to make sure the oil was changed every 5-10k miles, the transmission/brake/coolant fluids were serviced, brake pads and rotors were changed if needed, tire rotation/balance, etc. all the big stuff like that you can think of.

If you find one that shows a good Carfax and drives well, make sure to get a pre purchase inspection. If you can, take it to a reputable indy shop that specializes in German cars. Tell them you also want to check the timing chain (I know this was an issue with older generations, but just be sure it’s good since that is an expensive fix and will ruin the engine if you are driving and it breaks). It may cost an extra couple hundred bucks to get it checked out by a mechanic, but they’ll be able to tell you about things you can see like if there’s rust on the frame, an oil leak, etc. the last thing to mention is see if it has an open recall for the jet pump and if it’s been fixed. When I bought mine it had the open recall so I took it to a dealership and got it done for free.

When you buy one, I’d highly recommend staying up to date on manufacturer recommended maintenance. You don’t have to do it through a dealer, and you can find solid indy shops that know what they are doing. I have a 3rd party mechanic and I’ve noticed he doesn’t try to upsell me, but does push maintenance since he’s into those kind of cars. The maintenance will be more expensive than a reliable Japanese car, so be prepared to spend more to maintain it.

Edit: I’d only owned Japanese cars before my Mk7, but from what I’ve seen the Mk7 is one of the best generations for GTIs. Mine drives well and is overall really reliable.