Common sense prevails here.
450 hours is not excessive on a motor that's 10 years old, especially a 4 stroke. I easily put that many hours on my kicker in a year. How does the oil look? How does it start? Pull the plugs and take a look at them. How do they look? If they are new then that should be a red flag. How does the prop look? What about the oil in the lower unit? Is the oil milky?
Take a look at the bottom of the boat. It's alright if it's not perfect as long as it was repaired correctly. The bottom of my boat is no virgin, that's for sure. But each time it was damaged it was fixed properly.
One thing a lot of people seem to overlook is the trailer. Is it the right one for the boat? Is it broken? That is if it's a welded trailer, are any of the welds broken? Is the paint or if its galvanized, is the zinc coming off? How are the tires, including the spare? What about the lights? Although lights are not a make or break part of the deal. Because there are those who are having problems with the lights and there are those who are getting ready to have problems with the lights.
That is my

.
Let us know what happened.