The lack of hours on the generator isn't all that unusual, but it is something to watch out for IF it is the original one. Even if the owner changes the oil regularly, the generator still needs to be exercised under load.
If it has an oil cap with a built-in dipstick, see if the dipstick has disintegrated and/or fallen off. It could mean there are plastic bits floating around in the system.
I actually saw this on a genny. Looked like a dog had gnawed on the dipstick. Someone here mentioned that it's not unheard of for them to just fall off.