yep, so he has say a car worth 7000, but outstanding finance of 7500, therefore hes in negative equaity as his car doesnt cover the finance. so he will still owe 500quid on top of a new finance deal.
Did he put down a decent deposit? hes made a years worth of payments (which i doubt cover the interest) so really hes going to lose money.
again i could be wrong! just my experiance from a same situation.