Too old?

I dont know if this is the right place to post this (if it isnt i apologise) anyway im 17, 18 in april and i was wondering if im too old to start boxing? i already play football at a decent level and i was looking for a new sport to learn one which will help increase my fitness but also keep me occupied and not bore me.So i was talking to my friend and he said i was too old to box and that you ahve to start at a young age! btw im 5ft adn about 148 pounds i think? (10 stone 8 pounds) Cheers,lee.