If you are dead set on a BA to start with then you should also post the budget you have for the gun/upgrades/gear
if you are on a limited budget then the echo1 m28 would be your best bet.
But again like people have said this might put you off of airsoft by starting with a BA ( or it might not). Personally I have only used a BA at the last 10 games or so I have attended because I love it so much.
With that said, myself and the other guys that use BA's with me are very aggressive and we don't just sit in one spot and wait for people to walk by.
I would suggest getting out to some games and meeting people in the next few weeks before you turn 18. Ask to handle some guns, watch the people play, check out the field you will be mainly playing on.
Then when you get AVed check out the classified and there are lots of good BA's, AEG's and Gas guns at your disposal