A few months ago he was asking about financing a 1.2 Corsa for £5k. He appears to be 18.
I suspect then that this particular 523i is going to be a 'cheap' E39, 96-00.
I wish him all the best, they are great cars, but fear this isn't going to end well. These are just too old to be hassle free now, as DannyW discovered when he thought he'd got himself a 'bargain' 523i

At the very least it's going to do 270ish miles around town to an £80 tank of fuel.
He's posted quite a few threads on car buying, it's a shame he didnt post a 'Looking at a cheap E39' thread as you really do need to know what the minefields are when buying this and lots of us could have advised him.