So basically i’m a 22 year old man, who’s always loved boxy bmw’s and wanted one, so i came across an ad for a 04 plate bmw 3 series 318l, and for some reason the insurance is cheaper than on generic first cars such as ford fiesta’s, corsa’s and punto’s. I’m an 2nd year apprentice mechanic so i could handle most servicing items and routine work.

Basically the main point is, am i missing something obvious or is this car a great way to get a boxey saloon bmw on the cheap? 

Hi Sam and welcome. I have owned a couple of e46 3 series and they are usually reliable. 
the issues I have had is that the rear arches rust like they are made of paper. Don’t know why, but they all seem to be like that. 
I had a fuel pump fail for no reason and a ht lead fail. I replaced the brake discs and all pads easily and I changed the rear shocks by myself. So nothing is really a big issue. 
mim not sure if the 318 was fitted with vanos or nickasil issues? My 316 was fine, just needed a clean every now and then. Insurance is weird, my e36 was more than my e46 and the x5 is less than them both. I bought my wife a silly little street ka and it was nearly 2k to insure it! .... it got sold and we bought another 316 e46 saloon. 02 plate and the insurance was £600 fully comp.