The seller stated that there are no mechanical issues wrong with the car but I just want to look for red flags

One common issue is the heater / ac computer loses its mind when you disconnect the battery to replace it. Reprogramming it can be frustrating, and it requires the air conditioning to be working properly but you can do it yourself without any special tools.

The Body Computer has been known to cause the front wipers to not work at all or to work only on the low and high settings.

If you live in the north where they use road salt, check the front upper strut mount areas for rust. Stay away from any that have rust in those areas.