In my opinion b_light, not only do I agree with BigC and the others that you are way too young and that you should think long and hard about a pro's life in BB, but I think you should sort of re-examine your feelings on this drive towards bodybuilding that you feel.
You have already previously stated that you have no intentions of going pro, you just want to "compete in the lower levels". Honestly man, if competing for 20th place at sub-par events is your goal, you've already answered your question - you shouldn't take the risk and hop on the AAS bandwagon at 18.
Also, don't forget that anabolic steroids aren't the only drugs the big boys use. Insulin, HGH, Clen, DNP, even cocaine to help get cut. Diuretics to dry up pre-contest, laxatives, list goes on and on. Slin and DNP are especially dangerous. If you don't know exactly what you are doing, you could wind up in a coma from slin and cook yourself from the inside out if you OD on DNP. I guarentee you that 24-year old kid is on more than just AAS.
BB from what I have seen is not really glamourous. Remember what BigC said about homosexual favours for rich people? Absolutely true. Now, obviously Ronnie doesn't have to do that with a 500k a year olympia prize + a BSN contract, but think about what it took him to get there. Then think about the hundreds of others that aren't at the top,eyeing a dream they'll never have while some 140lb fag laughs it up with his cock 12 inches down their throats. Not fuckin' fun thats for damn sure.
I'm not telling you not do do it, because in all honesty, you won't give a shit what I or anyone else says on the matter. Your just another 18-year old looking for his magical ticket that will skyrocket him into the fast lane. Therefore, my advice is to think long and hard about your love for BBing.