How’s reliable is a 2013 panamera with 89k miles.

Porsche are not very reliable. And incredibly expensive to fix. I have dealt with customers not wanting to pay the part prices and complaining about the cost of labor also. Hard to get to components on these tight quartered engine compartments.

Reliability is probably pretty good, but repairs will be astronomical.

There is a good chance that it has been ridden hard and put away wet. Check the Porsche club to see if the owner has raced it. Also ask for complete service records and have a Porsche specialist check it out (not the one that the owner goes to).

Unlikely to have been raced. I instruct for several organizations and am regularly at the tracks in NorCal. I have never seen a Panamera being tracked. It is likely to be a reliable car, with some minor electrical issues over the next 20k miles like failing sensors. Porsches are usually in the top 10 of reliability surveys. If you can work on the cars yourself, you will save a lot of money. Shops like to charge extra for labor just because it is a Porsche and they assume the owner is wealthy.