I know the guy thats selling it so its not like some dodgey ebay or other auction site thing.
He had it up as a photo on his facebook and i asked how much he'd want for it.
Sounds dodgy, since the absolute cheapest 5150 I've seen was well over 550 euros (£485), and that one had very old poweramp tubes and no maintenance before selling.
personally i'd stay away from it even if i knew the guy - 400 bucks for a tube head that could survive a nuclear fallout...ehhh.... it might be the cause of a nuclear fallout
maybe ask the dude if u can get it for a test run for a day or two and take it to a repair dude to give it a once over - pay him 60 bucks or whatever. that way your covering your ass if something does go wrong