2000 Chevy Impala just bought this Impala. Hundred thousa

Intake vaccum test, compression test, fuel pressure test, cooling system pressure test, check ABS/ BCM/PCM with appropriate scanner for trouble codes. Make sure all the accessories work, turn on AC and make sure the cooling fans come on. Check your brakes, and brakes lines. Check your struts/springs (rule of thumb is if you push down on the car and let go it should come back up with almost no bouncing). Crawl under the car and check for leaks or signs of leaks.
That's a good start. Good luck