i bought my first DSM when i was 14 (awd black 95 R.I.P). great experiance and definatly helped with all the ladies back then too

. seriously tho, real time with a car you dont need to have running to get to work/school the next day is great experiance. i learned from taking it apart and putting it all back together. if your not 100% about your not abuilities i suggest getting a running car thats mechanicaly sound and starting from there. the main thing you have to think about is that car depritiate extremely fast. if you 14 1/2 now, you wont be driving for another 2 years. the average half-life of a new cars value in the states is 5 years. factor into that the money you would be making those two extra years and now your going from 95 civic si price range to old sti/evo price range...
when your 14 and look at a car that you could potentially own, its very tempting to just grab the first thing you see. i HIGHLY recomend you go look at atleast 5-10 cars befor you make your decision. decide whether you want a fwd, rwd, or awd. all three are extremly different and will be used for different things. do alot of research on each car. WHAT CAR TO BUY SHOULD BE AN ENTIRLY DIFFERENT POST. once u've decided u definatly want to buy a car now then come back on and ask what you should get.
you were on track with your mr2 and 240 comment, i'd stick with RWD.
IMO buy a decent S13 5spd. its a great platform to start with and parts are CHEAP. play around with it while your saving money and then swap in a SR20 redtop. it won't break any records or win any shows but its fairly easy and there is plenty of info out there on it. i love my S14 and the SR is surprisingly quick.
BEST OF LUCK!