600 is a great price.
At a minimum I would change the oil, radiator fluid, clean and inspect the carburetor, clean the air filter, check the tire pressure, inspect the brakes, lube the chain and cables if required, look for leaks in the fork seals and the rear shock seal.
If all that is good and it starts and runs good, then great!
If it runs rough, then check the compression.
If it's low, then a top end would be in order.
Have fun with it
