I used to know a lot about motocross (I'm assuming that's what racing you'll be doing)... The YZ's & CR's were from back in my day along with Huskies, Can Ams, Maico's etc. You need to talk to a winner. Go to a race then chat with the winner (NOT factory sponsored riders). It's obvious what bike they're using but you might want to ask what bike they WISH they had...along with finding out what spare parts you need to buy in advance... stuff like levers, cables...find out what breaks most often. Find out which dealers in your area give discounts to racers. How serious will this be? Will you train? Since you don't have a drivers license you'll need a place close to home where you can practice jumps and tight turns etc. You might want to go with a 100cc rather than a 125 because the 125 riders are going to be more experienced and older than you are. It'll be tough enough for a newbie to break into the 100cc class...good luck