i have a friend who fixes body work on cars and re sales them he says the car is worth about 17,000 but he will sale it to me for 9,000

its a 2005 330ci bmw with 80,000 miles on it
ive done some Research and i think its in-line engine which i think it good but why?
is it a good deal what do you think, im 19 will it work out you think

thanx i appreciate it